Amazing how nobody actually answered the question. The individual clearly stated they are not having any other issues with net connectivity no matter the application. It isn't until they start using SL that the problem exists. And so many of you just go on to quote LL on what they say they don't support. I too am having the same issue. I stream HD movies over my router directly to my TV while others in the home are doing pretty much the same thing at the same time. Bandwidth and my routers ability to handle it, IS NOT THE ISSUE.
The issue is, the wireless adapter on my PC and only on the PC that is running SL reports limited connectivity after only a few short moments of running SL. I can run all the other 3D intensive games and aps I want, with no issues. The issue is clearly with SL, not my PC, not my bandwidth, not interference from other devices in the area, not my routers ability to handle the bandwidth or any number of the silly examples I have seen given to this issue.
So who really wants to take a genuine stab at fixing the issue?