Full signal doesn't mean anything.
Click Start -> Run -> type in CMD
*black dos window will popup*
Type in the Dos-box : ping karoo.mweb.co.za -t
Reason you have to refresh your sites, is cause they ping timedout.
Now check your pings to karoo.mweb.co.za (thats a gaming server, and is always spot-on)
While its pinging about, move your modem around to different spots, closer to a window, 1meter to the left, or right, etc..etc (put it in one spot for 5seconds and check the pings, then move it to another spot etc.etc)
low pings = Good quality signal, and good signal strength.
(u can have full signal strength, but have poor quality signal and have huge pings hence the timeouts)..
If you've got a laptop, move around the house to check where the pings stays the lowest.
The other option is to get a external antenna that points to a Vodacom Tower :>>>
Hope it Helps