I have seen these kind of errors when the database is out of memory. The memory of a Mendix app is split in memory for the modeller and memory for the database engine. Normally these are split even. We had these kind of errors when there was to much given to the modeller and to little to the database engine.
File a support ticket is my advise. And you can check your monitor pages for your memory consumption and see if you see something out of the ordinary.
Regards,
Ronald