My domain is hosted by http://hostean.net, an ISP which I would really recommend. I realized that I needed a newer version of the Zend Optimzer to be able to upgrade to the latest version of my blog. So I sent an email to support, and after just one week they have moved my entire site to a new server running Zend Optimizer v2.6.2 without any problems at all.
So, if you need an ISP, I say again: I would really recommend Hostean…excellent service!