http://forums.arcgis.com/threads/312-Beta-10-Lock-Files ArcGIS 10: Lock Files
According to the above post the only way to delete these sr.lock files is to completely exit all ArcGIS programs.
When attempting copy &and paste of a recently used shape fileshapefile (with corresponding mxd closed) this error pops up :
It will paste a portion of the shape filesshapefiles, but not all of them.
I have both service packs 1 and 2 installed.