being disconnected all the time...

We are many users that use WLM 2009 version, and we all are being
disconnected and connected again, all the time...
This is a big problem while in groups, because some get the text, and some
don't.
We are using windows live messenger in our work, so we need somefixing here,
or we will have to change to another technology...
We have tested;
our network ok
others network ok
local machines are ok
repair have been run on both wlm and trend client, even reinstall of both
without any luck.

There is one questionmark however, and that is Trend Worry Free Business
Standard edition and its clients installed on our machines, but that is not
installed on all machines in the conversations, and they all have the same
problem...

Does anyone have any clue what it could be?