Hello Scschlee,
I had the same problem a few days ago after re-installing my Red Alert 2 game in Windows XP Pro (Service Pack 2). After a bit of digging around, I found out the solution to the issue.
You will need to change the short-cut properties for Red Alert 2, to run in compatabilty mode for "Windows 98/ME". This will stop your Skirmish games from ending abruptly after a minute of play.
If you are still having problems, I would also recommend downloading the latest patches for the game (Currently v1.006). I download my patches from : http://videogames.yahoo.com/gamefiles?cid=1990437526&tab=files&page=0&eid=-1
I install them in order of:
v1.001
v1.002
v1.003
v1.004
v1.006
I don't know what happened to v1.005
Anyway, I hope this helps you out.
Darren.