sweet mhary mother of Jaysus...

[classicdrogn]

Could be as simple as the other person having a bad day? Unless it's something like a tech support chat I'm not sure why you'd jump to "now it's a different person using the same ID." I suppose it could be someone's evil sibling/room mate/etc. too... so I guess generally what I'm saying is that if the previous interactions were positive, give them some time and see if there's a better explanation than malicious action, on their own part at least.