mounted NFS funnies

Hi,
For while now I have been having problems of peculiar kind with my SMC 
Prism54 card, when transferring
large amounts of data over scp, it works just find, but when I use NFS 
mounted partition to watch a movie with the card,
I get these stalls when signal goes to 0, and if I try to access any 
part of the nfs mount point, like say listing it, process hangs for 2-3 
minuetes. After which time it just undoes itself, everything completes 
and movie keeps playing after delay.
Same happens if I try to listen to set of directories mounted over nfs. 
Seems that after number of bytes there is a hiccup with the card and 
then it keeps going. May well be nfs mounting options - i use none and 
to what i have inspected i have very plain nfs kernel setup. To note, 
via wired ethernet this does not happend. If there some insight into the 
what is happening it would be great.
thanks,
pavel

Ps: keep up the great work.