Case update:
I was suggested to perform clean installation of Windows by one of your technicians. Rather than that, I decided to set up multiple instances of same Windows XP on same hard disk (different partition) using product recovery CD provided by local reseller. This was in purpose to test system some more.
On my old windows installation avast starts and even updates, but UI wont start. I do not see any messages about virus database update either, however avast.setup consumes some more system ressources from time to time and while I use uninstall option, the database is always up to date. No feedback tho.
I was suggested to install Security Task Manager from neuber.com by an Associate Professor from Institute of Computer Science of University. This program showed I do have avastUI.exe process running but inactive
I have tried to activate it using third part programs, but they fail without error message.
ON THE OTHER HAND:
As I said I installed new instance of same version of Windows XP operating system on other partition. I also installed most of programs I had installed on old version, including avast. In there avast works 100%. I do have graphical interface and I see notices about updates etc.
I also ran full system scan, including all partitions, and after that complete Boot-Time Scan. They resulted with 5 threats found (4 Trojan's and 1 worm). Those threats were eliminated.
When I retried scans the next day there were no threads found.
At the time I was testing my new installation I had avast removed from old one. When I was sure everything is OK with new one I returned to old one and reinstalled avast once again. Same problems - no feedback.
SUMMARY
Currently I have 2 instances of Windows XP installed on my hard disk, both equipped with latest version of avast! Free antivirus. I have kept both to finally find out what was the cause of inconveniences.
Both windows versions have all latest microsoft updates installed.
All registry keys in regedit.exe (windows registry) that are related to avast have been synchronized and overscanned. No difference found.
Even all services visible in services.msc have exact same startup settings.
Avast background services are working on both versions, but feedback (UI, notices etc.) is only available in old installation.
There is no vital problem for me anymore as we are using new installation these days, but I wanted to let you know that in case any of you would like to assist me find out the cause it is still possible.
PS! the same associate professor I mentioned above suggested me few years ago to use Spybot too. Here I was suggested to remove it from system. As a second opinion, what do you guys say about security task manager from neuber.com that he suggested me now?
(it's a long story, I hope I have kept it read-able)
