Have you seen this error in the current version? It's possibly a problem more with me running this game in a non-standard way. Do you mean switching commodity buy:sells? I haven't tried that but, as you see in the pic the nation is demanding some of those resources. I think it has to do with improper use of multipliers and dividers during a stacking routine which causes a double negative and returns the highest or lowest possible rounded value. Alot more common in a per second spreadsheet game like this. The error corrects itself at the month's end so I'm guessing somewhere along the line a necessary per-day check was changed to a monthly check for unnecessary process time results.
My next guess is that the bug was inserted into the VIC:R executable which is a shame since that version has some better functionality and script work. There don't seem to be any references of 999 prior to 2007 in search results. Odd how player's don't see how damaging this is to the game structure and have more demands for it being fixed. I suppose Victoria wasn't even half as popular as the other contemporary titles though.
I believe it has to do with removing the update per-tick routine which refreshes the GUI. Including the screen integer strings. The Revolutions coder thought it would be better for gameplay but, causes this database stacking error. Maybe it is aggravated by me running the program at 1Ghz in Linux using Wine. Vanilla Victoria 1.04 doesn't have this problem though but, it is kinda deficient comparatively.