Dropping bandwidth locally.

Hi all, do you have any suggestions as to where I should look for the solution to this one.
Now and again I get very low bandwidth being displayed in TVH. This is for locally recording DVR jobs so it shouldn't be network related. What else might cause this? A restart of the machine fixes it.... restarting the service does not.

It is a dedicated file sever with little load and working with a RAID 1 array.

Regards,