I notice this error in the event log quite often.  

The process cannot access the file 'C:\Inetpub\vhosts\mydomain\httpdocs\Portals\1\Cache\Pages\1136_ACABA51644A302FBB325E30E7931BAF8.data.resources' because it is being used by another process. 

It's not always the same file.  Seems to potentially happen to all modules/pages.

I think I get the basics of this error - a cached resource is locked by the file system.  But what might cause this?  And how to fix it?