I'm also experiencing desktop freezes on my machines with more than one active group:
System 1 xxxxxxxx Ubuntu 7.10 P4 3.0Ghz HT 1GB RAM (512MBx2) Intel Video
System 2 xxxxxxxx Ubuntu 8.04 Athlon 64 X2 4000+ 2GB RAM (1GBx2) NVIDIA GeForce 6100 (MCP61)
I'm also experiencing desktop freezes on my machines with more than one active group:
System 1
xxxxxxxx
Ubuntu 7.10
P4 3.0Ghz HT
1GB RAM (512MBx2)
Intel Video
System 2
xxxxxxxx
Ubuntu 8.04
Athlon 64 X2 4000+
2GB RAM (1GBx2)
NVIDIA GeForce 6100 (MCP61)