I'm suddenly having problems when setting variables in the server scope. The code hasn't changed, but they not available (variable not found) after setting them, which is weird. I'm not even sure where to start looking - any ideas?

Could a load balancer be in play where the server variables are set on server A, and the following request to check for the variables existence occurs on server B?

Bet ya five quid yer setting them on one server instance and trying to read them from another server instance.