I'd say the three things to to troubleshoot are:
1) Quality of signal into the box - any attenuators you can get rid of or boosters you can add?
2) Cpu usage on your pc. Try changing the priority of ggrab_mod to high when its running - it'll help if other processes are grabbing cpu time.
3) Networking bottlenecks. Also as a general networking tip I've found applying this suggestion has helped a lot:
http://gbpvr.com/pmwiki/pmwiki.php/Tips/MVPNetworkTweaks
1) Quality of signal into the box - any attenuators you can get rid of or boosters you can add?
2) Cpu usage on your pc. Try changing the priority of ggrab_mod to high when its running - it'll help if other processes are grabbing cpu time.
3) Networking bottlenecks. Also as a general networking tip I've found applying this suggestion has helped a lot:
http://gbpvr.com/pmwiki/pmwiki.php/Tips/MVPNetworkTweaks