mencoder grabbing problems with DVC100

Hi there
not sure whether this is the right place to post this… redirection recommendations highly appreciated…

Trying to digitise my VHS films with a pinnacle dazzle which is nicely recognised as DVC90/100. I can now - after a nightmare of sorting out the audio part that is, one nice glitch being that you quickly have to switch the audio channel off then on again right after starting the recording - watch everything without any glitches on mplayer. here is the command I use for that:

mplayer tv:// -tv alsa=yes:audiorate=48000:amode=1:adevice=hw.DVC100,0:volume=100:immediatemode=0:forceaudio=1

as I said works great no dropped frames or anything.
However: if I try to grab the whole thing with mencoder I get millions of dropped/skipped frames and the film really gets out of synch.

sudo nice --10 mencoder tv:// -v -tv alsa=yes:audiorate=48000:amode=1:adevice=hw.DVC100,0:volume=100:immediatemode=0:forceaudio=1 -o outfile.avi -ovc lavc -lavcopts vcodec=mjpeg:aspect=4/3 -aspect 4:3 -noautoexpand -oac pcm -endpos 01:17:00 -noskip

tried a few different options here but no real difference.
How come it works watching but not recording? Problem occurs on two different computers, one being a dual opteron 64 bit with 3G of first class registered ram and the other an amilo turion (dual core) laptop with 2G.
No performance issues, cpus are never running more than 50%ish.

Help or advice on where to get further information greatly appreciated.

Ah, yes: both systems are running opensuse 11.0 inux version (geeko@buildhost) (gcc version 4.3.1 20080507 (prerelease) [gcc-4_3-branch revision 135036] (SUSE Linux) ) #1 SMP 2008-06-28 00:00:07 +0200

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