IMP 3.1-RC1 and logout.php

[Matt Baran]

I upgraded from IMP 3.0 to IMP 3.1RC1 today in order to use Atif Ghaffar's 
excellent Multi-Panel patch with Turba support, and I'm seeing some strange new 
behavior on logout.

Hitting the logout link from IMP displays the normal logout screen (prompting 
you to login again) but the following errors appear on the top of the page:

Warning: Constant sid already defined in /var/www/html/horde/lib/Prefs.php on 
line 91

Warning: Cannot send session cache limiter - headers already sent (output 
started at /var/www/html/horde/lib/Prefs.php:91)
in /var/www/html/horde/lib/Prefs.php on line 91

Any ideas? Looking at this file just leaves me baffled.

Thank you,

Matt