This is the problem of the router that has been set to b/g mode, it got less range and many problems as I did.
The fix is:
log in to your router using PC : 192.168.0.1
Default username: admin
Password: blank or admin i think?

Then go to Advanced, Advanced Wireless, and change the b/g to b/g/n or n only if your house devices all capable to 802.11n

If you got iphone, then change the 20/40hz (Auto) to 20Mhz, because iphone is not capable to 40Mhz and get disconnect.

Then click save setting, then reboot, and anything get fine (Usually) 

Credits: rizvanrp,klseet, and someone else in this forums that posted this solution, I've forgotten the link.

Use the different username and password and try...
Username: operator
password: h566UniFi

I have same problem with my Samsung Galaxy Tab P1000...
It's working when I'm in office....BIZ5 using router DIR-615...
At home with VIP5 (router is black and printed TMnet on it), it's always have connection problem...download file always drop connection halfway, worse than my Digi RM68 3G plan....

But! Thanks to jaypah89  ...I tried his way...particularly change 802.11gbn to 802.11gb. (without n, changing 20/40GHz to 20GHz doesn't help)...

How? (This is for TMnet black router interface, DIR-615 looks different)
1. Go to http://192.168.0.1
2. Username: admin, password: (blank, just click enter if it's default setting)
3. There is a top horizontal tab: "Status, Wizard, Setup, Advance, Wireless, Management", click Wireless.
4. There is another left vertical tab: "Basic, SSID Configuration, WPS Configuration, Advanced", click Basic.
5. Mode combobox, change to 802.11gb.

Hope it works for you guys.