Funnily enough I did change my phone to a Nokia N900 a few weeks back.
I didn't bother loading the Nokia software with my previous N95, just accessed it directly from within My Computer.
I did load the Nokia software for this new phone, a bit of a waste of time as there is a load of stuff, particularly at the OVI store that is incompatble with the N900 and quite a few of the features within the software do not work with the N900.
Might uninstall it and see what happens.
EDIT. Unistalled all of the Nokia stuff and it is still happening, it is only doing it on that one site though, never had disconnect of BB conection on any other.