Upon advancing time by 5 days, I get this error:
I installed 6.30 using the AcidWeb's portable download, but updated to 6.40 and 6.41 using Steve's exe and database downloads, and not the 6.41 portable version.
Clicking OK results in 4 consecutive Error 91s then this same window again. The pattern of this window followed by four 91s continues for some time then the turn processes normally. This seems to happen every construction cycle since it happens once for every time I press "5 days".
I have met an alien race who decided to share geo and grav survey data but I (think I) have not located their homeworld.
The campaign is about 30 in-game years.
Restoring a save from prior to this then playing up to this point generated the same error at about the same in-game time.
There has been some shortened intervals prior to this error.