Windows XP HTTP, FTP and RDP problems

[Jason]

computer with XP Pro, internet connection is fine, get good IP, good
gateway, good DNS servers; can ping anything anywhere, can browse
internal network, windows auto update and anti-virus auto updates both
work;

HOWEVER, the computer cannot view any web pages (page just stays blank
with no error message and the flag keeps moving and the status bar
gets 4 green bars and no more), cannot ftp from command line to
anywhere, and cannot use Remote Desktop connection or VNC

Everything worked fine on Friday, Monday we VNC'ed in and were working
on something else and then out of nowhere VNC cannot connect and all
the above problems began.

Tried fixing the problem by reinstalling NIC driver and then even
updating to SP2. No luck and we are all out of ideas.