Well, I had close to 4GB free out the 20GB (maybe a bit less than 20%…). But since I suspected that was the problem too, I deleted some things and now I have 6.83GB free (about 35%). It didn’t solve the problem…
Anyway, I read about a solution which I haven’t tried yet:
I de-fragmented my media drive (D), which I gues I shouldn’t have done… That might have caused the problem. So I read somewhere I need to copy all the media files to another drive, delete it from D and copy it there again. What do you say about that ?
Another thing I was told I need to do (which I didn’t do during work till now) – when I work on more than one project – “hide” all the other projects’ media files (other than the one I work on) in files I creat for each project in the Attic folder. Is that true ? Could that also cause the problem ?
Thanks for your reply.