Anat,

Just to let you know - it will almost certainly be your ISP - I had this happen with an old ISP I used to use when I first started out.

I'd be going along fine then all of a sudden the server would report I had no disk space left. I'd complain, they'd do something at their end, then everything would be fine for a while.

Just thought I'd let you know that you're not the only one who's been in this position

All the best
Shaun