When i alt+tab out of fallout tactics, i lose the ability to chat.
I can only chat again when i restart fallout tactics. However when run on xp, its fine...any ideas?

Kind of strange. I have Windows Vista Ultimate x64 and I have ALT+TABBED sometimes and no problem. No problems when speaking people.
Have you tried executing the game in administrator mode? (Just go the icon, right click and select "Run as administrator")

yeah i've run it as admin
and im using vista home..i dont think there would be THAT much of a problem when it came down to running fallout.
And what do you mean sometimes have no problem?

he means that he sometimes alt + tabs.

yes i know.
what i mean is sometimes he loses chat and sometimes not?
BEcause i lose chat everytime i alt+tab and have to quit the match, restart fallout before i can chat again

Well, you can play in windowed mode.
Edit the shortcut and add to Destiny "-w".
I can't find any other solution.

Call me stupid but if you're playing fast 150k team deathmatch, there's no reason to ALT + TAB, don't you think?

what i mean is when im wating for a friend to come on so we can start a match, i usually alt+tab out into msn to see what's taking so long.
or in between matches.
Or sometimes yeah, he goes afk, so i just go back to msn or whatever.