I am in the process of upgrading my blogs to WordPress 2.6. That gave me a strange problem in some of my blogs, I got a blank screen when trying to access the admin part of WordPress. The strange thing was that those two themes (my own tweaks) that caused problem in admin mode worked well in the blog. I could not login but the blog worked.
Searching Google I found out that spaces at the end of wp-config.php caused blank screens but that did not solve my problem. After a tip in WordPress Support Forum I turned of plugins to see if they caused the admin issue. They did not but when WP-Spamfree was disabled I got an error message and not just a blank screen. The error message and Google helped me find an answer in Headers already sent. It turned out that my problem was caused by extra spaces in functions.php and after removing those spaces all worked well.
One thing confuses me though, how comes WordPress can handle the extra spaces in functions.php when in blog mode but not in admin mode?