Was this an attempted withdrawal from an exchange or gambling site (or some other custodial type wallet system on a website)?
![Huh](https://bitcointalk.org/Smileys/default/huh.gif)
If so, and you were just trying to send money to that one address, and you copy/pasted and the address ended up being modified, then chances are that you have the clipboard malware. You need to scan your computer for viruses/trojans/malware immediately.
You can test by trying to copy/paste various BTC addresses and seeing if they are modified when you paste them.
Personally, if the machine
was infected, I would be inclined to wipe the entire machine and reinstall the OS from scratch
![Undecided](https://bitcointalk.org/Smileys/default/undecided.gif)