I have heard of many people having this issue since ecSRO Updates they can no longer log into their characters, I believe this to be related to that item(s) may have been accidently removed from itemdata.txt in the newer files which existed in the last PK2s, but the Server still has record of this and is sending an ID which your client is trying to find but cannot, so crashes.
I have chances of finding this error better if someone is willing to lend a character of theirs (whatever level) that has issue related to this. I will be able to analyze upon login the characterdata packet and to check for items the player has, and then check if it is correct in the new files.
Regards
Eckoro