External References - box unchecks itself

Under System Options, External References, the checkbox nextto "Search file locations for external references" has started touncheck itself quite frequently here lately. When this happens, theassembly will open but some or all (depends on where the files arelocated) of the components will be suppressed and SW says it cannotfind the file referenced. It can be fixed easily enough by checkingthe box again, but I'd like to stop it from unchecking itself.

Does anyone else have this problem or do you know what causes it?

Thanks.SolidworksAssemblies