I was having a few problems with my set-up so i decided to do some investigation. I found that when recording multiple sky channels using WMC, that when i got to a fourth channel OSCAM would have the highest numbered viewer change from active to connected. On switching back to this channel it was know black. The same thing happens when i decrease the tuner count to three now on the third recording the first recording stops

My Set-UP

TBS 6981 DVB-S/S2 Dual tuner (driver:2.0.1.5)
Ominikey 3x21 (driver:1.2.6.5)
OSCAM (7242)
ACamd (0.6.1.8)
DVBLink TVServer (3.2.2)
Windows 7 x64 running Windows Media Center (WMC) - have UAC disabled