Network error. Server not responding... Windows Vista

[TarinTwisted]

I have a laptop and a PC that I run EQ2 on.My laptop is on XP Professional and my PC is on Vista Professional.No problems with laptop, however, with my PC that runs on Vista I sometimes am unable to login. Sometimes a reboot will clear up the problem but for the past 2 hours I have been unable to connect and I would really like to understand the problem so that I do not need to mess with this off and on like I do. I get past the launchpad but when I put my login name and password in it tells me network error and that the server is not responding and for me to check my login and password which I am sure is correct.Details...No virus or spam blocker software installedUp to date on patches for VistaFirewall is turned on (tried with it turned off and still did not work)I have even set the programs to run under administration modeI use a Killer Nic network cardI would appreciate some help.Thank You Very Much