It seems that several versions of Avast - I can only confirm it effects 6.0.1000 causes issues with networked files. Specifically that you won't see all the files in a folder on a network share if there are more than 90 odd files. The actual number varies for reasons I don't fully understand. Avast are working on the problem though.
I just got an email from Avast - they have a fix in beta that will be released soon,maybe today!
I just got an email from Avast - they have a fix in beta that will be released soon,maybe today!