I've been using Electrum for some time as well and never had any issues. Haven't downloaded anything suspicious. I copied and pasted the wallet address so no chance that I messed it up. It's completely different anyway. I tried setting up another payment to see if it was clipboard malware but it showed correctly in the preview as I had pasted it.
The only thing I can think of is that my e-mail was hacked and the wallet address changed to someone else. Damn