[horde] PHP ERROR: Cannot modify header information - headers already sent by

[Brain Drain]

I'm trying to track down this error in horde 4.0.13



Jan 31 16:05:01 phisch HORDE: [horde] PHP ERROR: Cannot modify header information - headers already sent by (output started at /usr/share/php/PEAR/Config.php:649) [pid 11316 on line 681 of "/usr/share/php/Horde/Core/Auth/Application.php"]

I already looked for the extra lines outside of <php tags and didn't find anything.  I was hoping someone here might know the problem off hand.