Yes. I used to get that quite often (well, once every couple of months). I never did figure out what the problem was, but in my case I noticed that everytime I told it to save, and it warned me it could not, it actually did save the model. So even though it said it could not, it really did anyhow.
But that was under version 5 and maybe 6. I really have not seen it pop up for me for about 3 years now though. so it might be a completely different bug.