Search Path not recognised?

[mtc.139414]

I use a script to update blocks in existing drawings (-insert blockname=\path\revisedblock) but on one of my machines this fails with "Can't find file in search path:" followed by a list of search paths including the one with the target drawing!
Anyone got any ideas why?

[jaberwok]

I'd guess it will be something silly like the filename not (quite) matching the name in the script.