Computer shuts down completely after accepting invite to view webc

it isnt my comp that has the problem but my friends, after i have invited
them to acccept to view my webcam after a few minutes there computer closes
completely down every time .also only yesterday after i logged into messenger
late evening i knew for a fact they werent online yet they were showing
logged in but had the words -WEB/ONLINE next to there name i could send an
instant messages to them but they never recieved them the next day are the 2
problems connected and whats the cure.i have removed my messenger7.5 and
re-downloaded messenger 7.5 and also mesenger plus again i have also done a
system restore to 7 days earlier when it was ok, and the problem is still
with them today and they have to reboot there comp again and cant use the
webcam without there comp shutting down.
i have xp proffetional and friends comp has XP home edition
also virus scans have been done in both computers and found nothing
also what do the words WEB/ONLINE mean next to a contacts name
PLEASE HELP
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Thanks Dave B