Occasionally out IT department decides to download new rulesets so our Barracuda firewall, and it then blocks access to Atlassian servers (as it classes them as download servers).

If the Sourtree client tries to check for updates whilst the update URL is blocked, the windowsupdates.aiu that gets downloaded is the barracudda blocked HTML page source.

From this point on, regardless of if we get the block removed, the update check fails. We have to delete the file to get the updater to recover itself.

This is easily reproducible. Shutdown Sourcetree, Put some scrambled text in windowsupdates.aiu and then try checking for updates.

The updater should be able to recover a invalid windowsupdates.aiu file.