[imp] Upgrade errors horde and imp

[John H. Bennett III]

Hello,

We are getting reports of numerous amounts of these error messages  
showing up in the logs:

Apr 20 16:54:10 mail httpd: PHP Fatal error:  Call to a member function on a
non-object in /home/httpd/html/horde/imp/lib/Block/tree_folders.php on line 65

Apr 20 16:26:32 mail ?? [7091]: PHP Warning:  Unknown(): Unable to call() -
function does not exist in Unknown on line 0

This is from an upgrade from horde 3.2.2 to horde 3.3.3 and imp 4.2 to 4.3.3

I know this may not be much to go on, but does anyone have any idea  
where I could start looking to troubleshoot this?  I can't duplicate  
this in my current environment, or on any of my test servers which is  
why I'm reaching out.

Thanks a lot,

John Bennett