After installing silverstripe (on a server I don't usually work with) I logged in as normal.
Today, i couldn't log in - the cms loading page (the one with the big logo) just stays.
I removed the _config.php file, reinstalled, logged in fine. closed the browser, logged in again - same problem - getting stuck on the cms loading screen...
finally found the following post and added 'Requirements::set_combined_files_enabled(false);' to my site config file...
doesn't seem ideal as i would like to use combined files... but better than not working!