[imp] signature empty after logout

[wirusy at e.lublin.pl]

>> Hi,
>> I have problem with saving signatures in my horde/imp/turba install.  I 
>> use version 4.0.3 horde, 5.0.4 imp and 3.0.2 turba. I tried  upgrading 
>> but then I had problems with dynamic view.
>> Do you have any suggestions what?s wrong ?
>> Pawel

>Without telling what your problem actually is, no.

Problem is that I can create new signature, even use it during the session 
but it occurs that there is no signature in preferences after logout and 
login again.
At first I thought that problem will disappear after upgrade (horde 4.0.15, 
imp 5.0.23, turba 3.015) but I can't use dynamic view in newer version (it 
loads listing forever - red info says "Error when communicating with the 
server." and "The server was unable to generate the message list."). 
Moreover in logs I've found:
[Wed Oct 31 14:13:20 2012] [error] [client x.x.x.x] PHP Fatal error:  Call 
to undefined method Horde_Session::start() in /home/httpd/newhorde/imp/lib/A
jax/Application.php on line 506, referer: http://server/newhorde/imp/
[Wed Oct 31 14:13:21 2012] [error] [client x.x.x.x] PHP Fatal error:  Call 
to undefined method Horde_Session::start() in /home/httpd/newhorde/imp/lib/A
jax/Application.php on line 735, referer: http://server/newhorde/imp/
So I have 2 problems, one with signature and second with upgrade. Can 
someone help?
Pawel