Problems using yahoo mail on Vista

I am having a problem with my yahoo mail on my home laptop,which uses Vista Premium i have reinstalled IE 8 a few times and havethe latest firefox. My yahoo mail was working just fine a few weeks ago. I now have service pack 2 for Vista installed and still i have problems.

When i log into my mail , i can read the emails but i cant create a new email, reply, download attachments or even forward an email.

I have tried asking yahoo for help and none of the trouble shooting steps worked and anyway it seems the problem is with my laptop because yahoo mail works on my work pc and my mobile phone.

PLEASE HELP i am desperate now because i need to use my mail. I use avast anti virus