virtualbox.org

Host: Mac OS 10.10.7
Guest: Win XP SP2

Bridged network functioned previously to permit file exchange between systems.

Have tried selecting other network options, same result.

Other potential useful information
TunnelBlick installedonnecedo VPN
Avast anti-vitus installed

virtualBSB wrote:Host: Mac OS 10.10.7

There is no such release, the last one was 10.10.5. Check again please.

virtualBSB wrote:Bridged network functioned previously to permit file exchange between systems.

Bridged has nothing to do with file exchange. It could, but not necessarily.

virtualBSB wrote:Other potential useful information: TunnelBlick installedonnecedo VPN, Avast anti-vitus installed

Uninstall them both.