Ok, thanks Andrew, deleting absolutely all log files from that folder helped.
(setting CDS_LOG_VERSION to pid or sequential did not help at all)
Also, one more question, since this topic is touched:
I have the following in my .cshrc file:
setenv DD_DONT_DO_OS_LOCKS
However, I see that it still leaves lock files inside cell folders after I am done working with them and close them, why?