Error: Surface temperature instability

[pat]

Hi folks, I have faced another problem (another time).

The story: I build a fairly complex model and failed to simulate due to error from the subject, then I asked experienced VE user and let him see the model, his advice was to redraw and simplify to let it be easier to simulate and also to do a check simulation during the model building progress to identify problems at early stages.

I followed the recommendations and built a simpler model (using prism tool mainly) and also carried out test simulation during process. After building two floors of nine I run dynamic sim to test and worked fine, I have saved the model as a separate model before attempted copying floors, then copied one floor (to have G-2 now). Run dynamic sim, worked fine, started changing names of corresponding rooms to express their position and stopped half way as the midnight hit and it was wise idea to get some sleep. In the morning I carried out changing the room names and when finished I run the simulation that failed with above error (did not happen last night, no changes to model apart from room names). I tried to delete the recently copied floor to see if will work but it did not. Therefore, I opened previously saved working backup to see what happens and the same error appeared. I must say that I have not even closed the VE, just used 'SLEEP' on my laptop to wake it up in the morning. Now neither of the models is working and all backups saved at different stages generate errors. Isn't it a bit weird?

I hope anyone has an idea how to address the issue.

Thanks, Pat.