MSN 7.5 Problems

Just downloaded the latest version of MSN Messenger (7.5). It’s coming up with this when i run the .exe:

MSN Messenger setup has failed with error code: ‘1601’. Please go to the MSN Messenger website to download the latest version of MSN Messenger.

Just wondering if anyone else has had a problem like this and could help me. Its the first time i’ve ever had a problem with MSN. I’m running XP Pro and Firefox is my default browser.