Hi Everyone!
Been super bz so I didn't have time to check in earlier but wow! It's nice to see the community 'spirit' still kickin'. Thanks to all who looked this topic up and for running through possible solutions, esp Shahz, for heeding my plea.
Right, just wanna share with you all, the problem's solved!
At first I thought it was something that ran deep, right down to the OS layer but for everyone who's curious (or who experiences something similar next time) the culprit was the app - EStrongs Security Manager!
I'd dismissed it as a cause earlier because the phone was functioning fine after installing the app and the problem only came up a few days later. Trawling the net for similar symptoms also revealed that lots of people were also experiencing similar problems. I also thought there was a flaw which prevented the phone from remembering the default choice of home screen, made even more puzzling since I didn't have Launcher Pro, ADW, etc installed. HTC's official response was also that all HTC Android phones 'only come with HTC Sense' (duh, isn't Sense just a UI layer on top of bog-standard Android?).
Anyway, after uninstalling EStrongs, the problem disappeared immediately and HTC Sense no longer appeared as a running app in the task switcher (home button long-press).
So remember folks, if you're experiencing the 'Complete Action with Home/HTC Sense' dialogue, it's because of an app you installed (although the app in question will differ across incidences).
For the record, I'm still new to Android so I wanted to get to grips with it first and enjoy the 'out of the box' experience before skinning or tweaking the OS. Gotta admit though, there's some sweet looking mods around (eh, whitegoh? ;p ).
I also consider bloatware to refer to crap applications which I have no intention of using or which slows the system down significantly when they don't need to (I'm looking at you, Creative, and all those extra 'utilities' pre-loaded by some notebook brands). Some might consider Aero for Win7 or even the standard WinXP UI bloatware, preferring instead the Win2k Pro experience (yes, I know some of these people ;p). As long as it doesn't affect the functionality of my device or even enhances the user experience, I'm happy to refrain from categorizing Sense as bloatware. Just wanted to chime in on the discussion

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So happy ending, thanks again everybody!!!
This post has been edited by The Scourge: Sep 8 2010, 12:12 AM