Added En-queue Delete/Rename support to the local browser right-click menu.
Fixed a couple issues with the secure connection indicator on the status-bar where the actual status didn't always reflect the indicator status and clicking in the indicator area could sometimes trigger the certificate display when the indicator was not displayed.
Fixed an connection attempt timeout issue, when connecting to a SFTP site FlashFXP would report a transfer failure error even though no transfer was in progress.
Fixed FTP active mode connection issue that could sometimes result in a failed connection.
Changed the transfer complete status line for transfers completed in 1 second or less.
Changed the queue completed "transferred" status line to only be displayed if a transfer is performed and the average speed is now based on the duration of the queue.
Reworked the internal TCP/IP routines to provide improved performance as well as to scale based on the system hardware.
Some secure FTP servers require a delay after issuing the CCC (Clear command channel) command before they'll be able to recognize clear text, In some cases the delay used by FlashFXP wasn't long enough, this delay has been increased to improve compatibility. Most noticeably FlashFXP would appear to hang during login when sending the CLNT command because this is the next command sent after CCC.
Optimized the server file cache 'save to disk thread', when the internal cache becomes full the data is then relocated to the disk drive in a batch mode but the method wasn't optimal causing the UI to appear frozen during the relocation.
Reversed the changes to the 'edit file' feature that were done in back in build 1548.
Fixed HTTP Proxy connection issue where in some cases 1 byte of the stream data was mistakenly treated as part of the HTTP headers.
Simplified HTTP Proxy connection failure error messages.
relocated the "Show active edits window when editing" option to the "View and Edit file" section.
Fixed an OpenSSL issue with some servers when using AUTH SSL.
Fixed remote tree-view icons lacking proper transparency, this was noticeable with a custom background color or if disconnected.
Remote View and Edit now use separate temporary folders so that viewing a file after an edit doesn't trigger a file change notification to upload.
Added 'Schedule At' under Queue on the main menu, previously this was only available via the queue window right-click menu.
Fixed bookmark synchronized browsing issue.
Fixed list and file transfer timeout after 2 minutes.
The custom TCP/IP Buffer sizes weren't being applied correctly. If you're seeing poor performance now please reset your TCP/IP buffer size to default.

Changelog
In this release I eliminated a lot of overhead and unnecessary file operations that were performed prior to each file upload and download. These changes combined with code profiling and optimization have resulted in huge gains in performance and faster transfer queues. And it doesn't stop there, I eliminated UI drawing overhead in numerous places that was causing a performance bottleneck and reducing queue efficiency, I also reworked the task scheduler to disable most of the UI drawing during a schedule since the schedule runs minimized to the tray without user interaction. The performance gains are quite amazing to say the least.

I conducted a couple different test cases and I've outlined the performance gains below. Most gains are from uploads and downloads, with site to site transfers showing very minor improvements.

Test case #1: I perform a nightly FTP upload from my machine to a LAN based FTP server where I upload only new or modified files. This queue contains roughly 250k files and the vast majority of them are skipped. In version 4.0 this process takes over 2 hours and 20 minutes when run as a scheduled task. In this new build it takes 10 minutes when run as a scheduled task and about 20min when run directly with the UI visible and active.

Test case #2: This queue consists of uploading 3k files, downloading 3k files and then transferring the 3k files from site A to site B and then from site B to site A. In version 4.0 this takes 6 minutes and 40 seconds. In this new build it takes 6 minutes 29 seconds. Not a huge improvement but it depends on the situation.
The check free disk space on download feature wasn't properly checking the free space when creating local directories during download which it does now.
I accidentally left a couple debug beeps in the previous release good thing too, The debug beeps indicated that the internal folder structure table was out of sync after performing a remote file delete operation due to an incorrect sequence of commands. This has been resolved and the annoying beeps have been removed.
When adding a new folder bookmark if the name of the bookmark matches an existing bookmark you're now prompted to confirm replacing the existing entry, Previously it would replace the old bookmark without warning.
Fixed a bug on the Attributes (CHMOD) dialog when entering the folder mode directly into the edit box the value was ignored.
In v4.1 Build 1569 I discovered a nasty memory corruption bug that caused havoc with internal memory structures, many of the unusual problems some of you have noticed were caused by this. The memory corruption occurred due to a very unusual chain of events caused by a code change I made to improve the performance of the remote folder navigation. As far as I can tell many previous beta builds are effected by this issue. I urge everyone using a 4.1 beta to upgrade ASAP.