I had that in November last year. Then one by one the friends re-appeared again. Except one who seemed to think I'd taken a huff.
The problem then and it hit Facebook too, was down to a virus called Koobface. Sometimes you'd get a message saying you've been spotted or tagged in a video and click the link which, sadly, let the virus attack your address book and whatever shares the same password as your Bebo page. Capable of sending nasty messages to friends but apparently from your account.
Upgrade your anti-virus protection. Avast is a good one. Or AVG. Both free and down loadable. And please, please, please do not use the same password for everything.
Best wishes xx