Christian and all,
there is indeed a problem. It is the same problem as we had yesterday when the clean-up script complained (and actually refused to work). It is rooted in the backwards-incompatible changes in the structure of the session files. This is my fault, and I must have thought about it and its scope beforehand. Yesterday I have fixed part of the issue, but not all of it.
At this time here is what I have to say: I understand this issue and I'm working on a fix. I estimate that I'll get the fix either later today (in about an hour from now), or tomorrow.
I'll report as soon as I get it done or have other news.
-ivan