perhaps their site isn't sanitizing the field inputs? if you are pasting an address sometimes non-visible characters (e.g., tab) are pasted as well. the website can take steps to strip out any undesirable characters, but when that isn't done, then the field validation will fail as those characters are not vaild as a bitcoin address. one way to confirm that is truly what is happening is to paste the address into notepad or some other tool that doesn't keep those special characters. then copy the address that you just pasted and try that address into the btc-e form. (or, simply type manually the bitcoin address.)
one other reason that wrong address might appear is if the bitcoind the site accesses is failing.