I'm applying this to oldstatus now that the string freeze is over:
Patch #1223021 from Jason Roth (jroth2)
Fixes Bug #1222552
"As described in bug report #1222552, gaim will disconnect the current msn session and corrupt blist.xml when you try to add an msn screenname with a space in it" -- jroth2
I reworked this quite a bit. Stu suggested using gaim_email_valid() rather than just checking for a space. I took this advice. I also made it display an error message instead of silently dropping the add request.