You say you can use Limewire ok? My guess is, you have one, if not more Trojans on your system. Forget Norton etc virus checkers, these modern virus's/maleware/exploits are way smarter than they were 2 years ago. Now they can bypass your virus checkers, firewalls etc.
Go to Control Panel, double click the Firewall icon, then the Exceptions Tab, see what programmes are listed. Uncheck everything (and I mean everything) except SecondLife.exe and SLVoice. Now try loggin into SL..... if that works, dump Limewire, in fact dump it anyway, its a great way to become infected and some kind sole to steal what little ram and connection you currently have.
On a side note: Maggie, you dont offer much assistance to the issues, thats the 2nd post I've seen of yours quoting going to an internet cafe... you own one?