Magento Post-upgrade: Illegal scheme supplied, only alphanumeric characters are permitted +SOLUTION

So one of our customer’s sites started throwing this error message immediately following an upgrade. Illegal scheme supplied, only alphanumeric characters are permitted

Turns out 1.6.2.0 doesn’t like anything other than a-z and 0-9 in the store run code and the customer in question had underscores (_) in the store run code.

The simple fix was to strip it out and alter the url to store code logic to match.

Hope this helps someone else out there. As to why someone at magento thought this was a good idea is beyond me though.