Les, might give this free sysinternals utility a try, we're currently using it to debug an IE6 frezzing problem ... it dumps open file handles by process etc ... not sure if it works on a file on share though ...

SysInternals Handle Utility

We kinda use it like:

F:\>handle

handle.exe pid: 2960 TASSIE\Shawn.Tassie
48: File F:\
b8: File F:\del.me

-Shawn