I've tried a search but can't find anything that matches.

I JB my iPhone a couple of months back and all has been fine.
The last week or two, I'm having problems with my wifi connection. Will try to explain:

Connection is working fine, I go to work and come back home and the phone won't pick up the connection? The status bar doesn't show any Wifi signals, yet if I go into settings the wifi is on and connected to my router.
If I go into SB settings, the Wifi icon isn't on, I turn it on and the icon loads briefly and illuminates, but still no signal bars. If I exit SB settings and go back into it, Wifi icon isn't on again.
All this time my settings are still saying Wifi is on & connected.
If I then respring through SB settings or winterboard I then get the wifi signal bars at the top of the screen, but as soon as I load either email or Safari, you can tell it doesn't work as the speeds are slow....

As soon as I reset the phone (sleep & home button), the signal bars are there, connection works fine and the icon in SB settings is now highlighted.

Having to keep hard resetting the phone everytime I go out and come back home is a pain in the arse!!

Any ideas...?