OS X Webdav connection issues

We use webdav mounted on local machines using Rumpus file server app.

Thunderbird (Ver 3.1.20) image attachments are directly saved or opened using Preview (Version 3.0.9).

On some machines "Save" or "Save As" to mounted webdav volume works fine. On other machines at different locations either Thunderbird or Preview just come up with "Not Responding" under Activity Monitor and spin their wheels till forced quit.

Local machines are all ageing PPC's running Tiger and app versions are the same so cannot work out where the issue might be.

Any suggestions as to where to investigate would be much appreciated.

Rumpus is running on Mac Mini (Lion). Also, Littlesnitch is enabled but ports open and some machines connect fine and so do the ones with issues when just dragging and dropping - just through Preview and Thunderbird that we have the issue.

Thanks

Michael