Hi Jetti - the log snippet appear to show an issue with an 'A*' requestor (a 'Service' Requestor : in this case relating to a File Listener) rather than a 'H*' requestor (a 'HTTP (browser)' Requestor).
But may the two are inter-related.
You mentioned this :
Not sure whether any of the developer changed any setting in requestor type
Is something that could have happened you think ?
You might want to consider logging an SR for this....
Marty Solomon reported Bug-208976 before, which caused him could not login the PRPC at all, but in that case he was trying to configure the system so the number of login sessions per operator can be limited.