The debug system logs led me to believe there was some form of memory issue initially. Greater minds than mine (well, at least people more familiar than I with linux memory management ) on the ATV forum seemed to be pointing to memory fragmentation issues so it was there that they were discussing the possibility of flushing cache to limit the problem.
I do understand that linux tries to keep as much as possible in memory - the strategy being that it's much faster to retrieve data from RAM than from a device I/O. Something in this particular situation with Gigablue seems to interfere with the normal memory management where a number of contiguous 128k blocks are needed for video handling and were not available due to the file reading process using up almost all the RAM. Forcing the system to keep more free seems to work around the problem. I'm not flushing the cache using the plug-in, though. Just reserving 20480 kB of free memory.