@wild_Willie2: I thought that wab battery too on the beginning... But before my problems with reader I was able to read ~1000 pages without charging so I assume that battery was working quite good. And also I charged fully PRS overnight using standalone charger (not PSP but similar).
It looks like reader is in somekind of 'processing' mode. I read that yellow led points that processor is working. I had similar issue before but then yellow 'automagically' started to blink sooner o later and I was able to do the reset procedures.
I stored all my files in internal memory of reader not on the card. And I mainly used .lrf (maybe I had 2-3 only).
When I'll be able to revive him I will pu t only one book to memory and check if any problems occure.