I've run into a similar problem. I've migrated my site to the live server and now when trying to access mydomain.com/admin it hangs on the "Silverstripe" logo page and won't even launch the admin interface.
Judging by all of the questions, it appears that site migration problems are not uncommon. I wish there was more definitive documentation for migrating a site from one server to another.
If you have resolved your problems please let me know what you did. Thanks!
I experienced a fresh 2.4.4 install having trouble with the admin section only - taking a very long time to display and when (or if) it did display the admin section, clicking on the save button would result in it continuously displaying the wait symbol. The following fix resolved it for me: http://www.silverstripe.org/releases-and-announcements/show/15267