Vista - Messages Not Being Delivered

Hello

I am having a problem with one particular contact (that I know of,
there could be others but I am unaware). This contact seems to be not
receiving all my sent messages, as well all their messages are not
getting delivered to me. Neither of us get that bounce back message
“message cannot be delivered...”. They just seem to be lost.

After testing on different machines, I think my setup is at fault. The
problem seems to disappear if I am using another computer. I am
currently running WLM version 2009, build 14.0.8050.1202, on 64 bit
Vista Ultimate. I never seemed to have this problem on versions
previous to the new messenger style (8.5 and below). I started to
notice this happening after I installed the beta for 2009, although it
still happens with the current version.

Is this a common problem? What types of issues can cause this? I
haven’t been able to find much information searching through the
archives.

Any help is much appreciated.

Thanks