Avoiding locked files - like ethumbs

Hi,
I have a media library at home and I use FS to share it with my portable.
My portable runs Media Center and creates those ethumbs file. Unfortunately,
every now and then, FS tries to sync that file, but MCE has it locked. This
generates a dialog box that I have to either cancel or quite MCE to get rid
of.

Is there anything else I can do? I'd really just like FS to either ignore
the file and not sync it, or ignore the error and try again later...

Cheers,
Gordon.