Hope you're doing well Ollie, been working through the updates you've pushed out at they've been spot on - I no longer have any plugin file hacks now! :)
One thing I have noticed though, in my WordPress Network (not sure if it does the same on a normal install) if you click on Maintenance link under the options the site crashes. You can see a picture of this here. Note that the site title and admin bar vanish as does the menu options for WPSQT.
The page doesn't crash as such, it just never loads. It's like it's entered a big loop or something. The front end of the site also fails to load whilst it's doing this. However other sites on the Network where the plugin isn't activated work okay. This crash/continual load lasts about 3 minutes, then comes back to the Upgrade page at last, saying that it's all up to date.
Nothing comes out in the debug log during this time.
I can't test this on a normal WordPress network, so I can't verify this theory, but could it be because I have the site running internally as an Intranet site with limited access to "the world" perhaps it's timing out after trying to reach a certain destination. It does have access to the WordPress domain for updates etc though, unless it's looking elsewhere? That is, if that is even the problem :)