It may be worth taking a look at your Remote Desktop connection options.
After you have opened Remote Desktop Connection, select Options >>
Navigate to the Experience tab... is Reconnect if connection is dropped
Navigate to the Advanced tab... is Do not connect if authentication fails
selected in the Authentication options combo box?
What version of Remote Desktop do you currently have? You can find the version by first loading Remote Desktop Connection and then clicking the RDP icon in the title bar followed by selecting about...
Lastly, I would attempt to reload your Remote Desktop Connection (Terminal Services Client 6.0) for Windows XP (KB925876) available here: http://www.microsoft...;DisplayLang=en
Also you stated after your connection parishes it cannot connect again... Is this permanent, or does a reboot fix the issue?