ejabberd + ldap weird issues

Guys,

I am experiencing weird issues with my ejabberd install where I use multiple vhosts and all authenticate via ldap. ejabberd 2.0.1.

1. When u first start ejabberd server - works great everyone is able to connect, authenticate against ldap, etc.
2. Then u let it run for (from my observation approx. 1,5 hrs), u try to login again and it just trying to connect forever, then eventually asks u for pass again, and the same story when u enter it. However when u do quick ejabberd service restart - logs u in the very milisec, and then works again for another 1,5 hrs. :(
3. I must say I was listening for traffic between jabber and ldap with tcpdump... hard to see the consistency to make assured judgments but but it seems like packets are not always sent by ejabberd to ldap after 1,5 hrs (won't say 100% though).
4. I can see a bunch of connections established from ejabberd to ldap via netstat, ejabberd is listening on required ports, and service is running, except it is not working correctly after 1,5 hrs after restart.

My ejabberd ldap config is fine (proved on other ejabberd servers). Network topology -
ejabberd is in dmz, ldap is in lan, both connected through cisco firewall.
Could it be mnesia db corruption? Although I did backup/restore new version.... and in that case I assume it would not start at all.

Thanks