Same problem.
This is a bug. It has nothing to do with the speed of a system. I played the game for a week solid, and poof. This just popped up, ruining my game. I cannot change leaders. This is only for land units. I play Germany. I hardly want some zero skill dolt handling My new King Tigers While Von Kleist and Guderian sit in the pool. This and the disapearring units have disgusted me into not playing anymore. Play date is around 1943. I use Win XP. Athlon 1.2 GB Thunderbird. 512MB of DDR, 64MB Geforce 3. I have the savegame file. There is also a "database mismatch" error. I have no clue where this came from. If there is a related issue, I use paratroopers, with (Historically) Skorzeny, and Student in charge. I hope this gets fixed. Its no fun playing a new game for a week to have something like this happen.
This, I am dissapointed to say, is the second time Ive gotten a bum Strategy First produced product. The First was WW2 online. I won't be buying anything else with the SF logo on the box.