I can't reply to mail in Yahoo

Hi,
Thanks for being here, I stumbled across this site by accident, but have been really impressed with the level of expertise here.
I have XP, but for about a week have not been able to reply to mail in Yahoo. When I click on 'reply' there is a small yellow error message in the bottom left hand corner of the page saying "error on page". I had installed Norton 2005 anti-virus and ran a full system scan. It found 8 things (including Trojan.goldun.1) but deleted them.
I'm running free Zone Alarm too. Do you have any ideas or have heard of this before?
Thanks for any help.

 

Just to let you know, thanks anyway but I solved it, by deleting all cookies, temp files and re-booting. How easy was that...?