IE Problems

I have a issue where I have two identical machines Dell Inspiron 8100’s with XP Pro on and version IE 6.0.2800.1106, with SP1 on thro a network connect to the internet via ASDL.
Although I am unable to logon to a web page,
This is a secure site which I have a log on ID for but when one machine logs on its starts to log on but then goes no further than a lon on in process screen. The working machine logs on with no problems atall.
Can anybody make any suggestion as to what settings on the PC or network somewhere that could be resulting in this error