Ok I've tried this upgrade several times now and each time the same thing happens.

First time, it all worked fine, then a day later I went to the site and I just got a time out waiting for the site to load, and on the server noticed hundreds of php.exe processes had been spawned.

So I restored the site. Now each subsequent upgrade the same thing happens. As soon as you have the upgrade complete notice and click to return to the forums you get nothing, just it trying to load.

Has any requirement changed with version of PHP or MySQL with this upgrade?

No requirement changes. Try going into your templates/compile folder and deleting all of the .php files in there.

Thanks Rick, ill give it a bash, does that suggest you have heard of this or come across something similar?

Yeah, I remember working with someone else either on the forum or in a support ticket where something similar to this was happening.

No dice.. still doing the same thing.

If you want, go ahead and open up a basic support ticket and then I'll see if I can debug what's going wrong. I'd need FTP info to your server.

Ok will do