a recent move by yahoo limits  the number of id's that may log in on an ip. that means if mom logs in, then dad, then junior,  your going to need to reboot before spot can log in. if spot tries..... he will probably see that smirking smiley on the error screen.  again, simple fix, just reboot. that means click start, then shut down. wait 30 seconds, then turn comp back on. there should be no need to clear cookies. but that doesn't hurt either.

another problem has been  the booters, spammers, scrollers, and general idiots that seem to be rampant lately in chat.  when they flood the screens, it can cause messenger or chat to freak out, and cause that chat error. again, simple fix, try rebooting/ reloading the chat  option (java or messenger)  or even reboot your comp.

cant log in? get invalid password or username? clearing cookie, and reinstalls will not fix this. you were spamming, had too many ids open, or were doing very bad things. WAIT 24 hours for the block to clear and should be fine. think this doesn't apply to YOU? http://add.yahoo.com/fast/help/us/edit/cgi_feedback  and explain to yahoo..

other possible solutions include  

checking windows updates, 

updating virtual machine, replacing chat files, 

cleaning temp files, 

and the ever popular scan disc and defrag. 

and don't forget the reboot.  

good luck.....

the most troublesome chat error has been the one suffered by cable isp users and may be because of the scrollers, spammers, booters. .......

if you can log in then with no error, that's what happened.

when those idiots post certain links, or objects in chat , or even via email, once reported~ they actually can be subject to an ip ban.  the most prolific spammers can cause yahoo (or other chat server)  to ip ban a a series of ips. so if your ip on cable is ( make believe number here......i know they only go to 256...) 999.999.999.999     and the spammer is on 999.999.999.888   and yahoo decides to ban the spammer. ....... they tend to ban all ip connects from 999.999.999.000 to 999.999.999.999 ..... 

so innocent cable using chatters get caught.  =o(  why? because your ip is static on cable, it stays the same. dial up users get a new ip each time they dial in.  that sux! so.... if you use cable, and have experienced the dreaded chat error, try calling your cable isp, and ask for a new ip. explain it best that you can, and ask if they can investigate it at their end as well. if they are spamming, i'm sure the isp will be thrilled to cut them off.