NAV 2009 RTC Client Randomly Failed to Connect

This morning I had one strange issue while trying to connect my RTC client to data base.
Immediately after starting RTC client I got this error:

Type: System.AccessViolationException

After trying to give access rights to Microsoft.Dynamics.Nav.Client.exe, and giving extra admin rights to current user nothing did the trick. Then I started thinking that maybe there is problem on Service tier. Now it was time to change setup of services. I noticed that some of services are running under "Local Account", and some under "Network account". This was obligatory because I have more than one NAV Services. Since "Network account" gives so much trouble and is really delicate to maintain i decided to change every one service to run under local administrator account. After I changed this setting and restarted services everything went through.