Internet password keeps being requested

I have a new macbook which works fine BUT.. my internet connection here is unpredictable and every time it fails momentarily (4 or 5 times a day) I keep being asked to enter my password to reconnect. My router is a Thomson TG585 with WPA+WPA2 security. Having just migrated from a PC which just reconnected automatically, I cannot believe that the macbook doesn't do likewise.
Any assistance would be appreciated.
Steve

Hi Steve, sometimes, but not always I have the same issue. I suppose it's a software bug, if I turn airport off and on again, then my MBP connects without asking for password. I don't know if it helps you or not, but when I'm feeling lazy writing the password I do that.