Do you have more detailed information about the PHP5 that's available on your systems? In particular, do you have support for PDO, with the proper drivers for MySQL? My current host supports PDO, but doesn't have the MySQL drivers for PDO installed, and won't be able to get it installed for another 6 weeks or so. This has put me in a bind with an application that I'm developing for a client that needs to be online in the next couple weeks, so I'm exploring other hosting options.
Actually, if there's anywhere that I could see the output from phpinfo() on your servers, that would be really helpful - the installed PDO drivers are normally listed at #module_PDO, but it would also be nice to see what other modules, etc. are available.
Thanks!