Do you get these error messages when the users are entering the data, or when you try to compact the database?
I have the same problem with some of my larger databases and find that when I try to compact I receive this error. It is always that I have run out of space on the shared drive. I copy the database to a larger drive, ie c: or other local drive and compress there, then overwrite the old one with the compressed version. I then archive the compressed version I have on my local drive (Just in case of problems).
My guess is not enough room where the database is located.