Windows Live Messenger censoring URLs?

Today I pasted this link on an MSN Messenger group chat hosted by a Windows Live Messenger user: http://www.utorrent.com/download.php. My connection to the group chat was immediately terminated.

Then I pasted the URL on a single conversation with the same person. Again, I lost the connection.

Then I nuked the download.php portion. It worked.

Then I nuked only the .php ending. It worked.

Then I tried with somethingelse.php in place of download.php. It worked.

It bears to note that I'm using a multiprotocol IM client called Kopete. Not any of Microsoft's products.

Judging by the speed of the connection lost messages, it doesn't appear to be local or in the topologic vicinity of my network.

Is this some sort of virus prevention scheme? Has someone experienced this as well? Please let me know