When I use a nexus to build a probe, it shows that the probe is in the process of being builded, but the little green bar of the progress doesn't move....
In other words, it takes infinite amount of time (literaly, infinite, meaning it wouldn't build) to build a unit, the same thing happens with my gateway, but my other factory buildings works just fine....
Now some things that I did and didn't do:
1. I didn't change the building time of the probe
2. I did set probe into a zerg unit in datedit
3. I did set the nexus and gateway into a zerg unit in datedit
4. I set my stargate to a terran unit... and it worked fine, unlike my gateway and nexus
5. That's about it...
None.
Zerg buildings can't produce units without a special .exe edit. It's called "Train Unit".
I've faced similar problem, but it wasn't connected with alignment/race change. I've added unit build button (FG) while factory was in transit. You could buy it, cancel button in order-menu appeared, and unit icon with progress bar in the middle, but nothing more happen. Later I've changed my mod to suit my modding skills, but I'm still interested is it possible to build in terran factories, while they lifted off.