Address Book Hi-jacked

Hi, computer masters, Best wishes,
From this morning when I opened my yahoomail account ,whenever any page opens before that one dialogbox of Microsoft Internet Explorer appears stating
" A script on this page is causing Internet Explorer to run slowly.If it continues to run, your computer may become inresponsive.Do you want to abort the script ? "
I have two options either yes or No. I clicked once yes and next time No.
But then also this window appears every time when next page is opened on yahoomail. When I tried to open my address book it did not open.The window says did not find the addresses or url.
Appearing of dialog box really irritates me. Why it started ? Is it a bug or something else ? How to fix this problem ?
I am using win98 OS and internet explorere 6. This problem is with yahoomail only and not with any other sites.
Your help and guidance will be appreciated. Thanks and regards.
mishrarc

 

Sounds like spyware. Moving this thread to the security section.