Worsening Wireless, and no Wired

Ever since I switched from Bell Sympatico DSL to Rogers Cable Internet, my laptop refuses to connect by wire to the Internet via the router. However, I can connect to the Internet via the router on the PC.

At first, it was not a huge problem. But these past few days, connectivity has been terrible, going linkdead every 15 minutes. Sometimes the wireless light would just be off... and it always says my network adapter is not installed, even though I have done nothing to disable it (except to repair the connection).

Was there something I had to do when switching from one ISP to another? Because it's as if my laptop doesn't recognize a wired connection anymore, even when connecting directly from the modem to my laptop.

So far all I've been doing is rebooting both laptop and router... but it's gotten so unreliable, and only adds to my aggravation.

Hope someone can help. =/