WordPress & PHP5

I received an email from my webhost today advising me that they would be upgrading to PHP 5 immediately. They did not expect any problems.

An hour later I attempt to load up my wordpress and expression engine powered sites, and get a file download box, and not my site.

They basically tried to tell me that it was just me unable to access my sites, but I’ve called on a few friends across the globe and they cant either.

Are there any current issues with wordpress and PHP5?