Spam is sent from my yahoo account via various computers, is the account itself corrupted? Password

Use various computers, all anti virus and spam checked, to log into our yahoo account. Approx 1 months ago our whole contact list disappeared. The 'sent items' show spam messages sent to contacts and I receive daily failure notices e.g. after registering online with my yahoo email address via any PC, I receive emails from postmaster/mailer-deamon etc about failed deliveries which were trying to sent spam to new contacts as below.

I changed password twice, no improvement, assume yahoo account itself corrupted, please advise

latest failure message:

Date: Wed, 30 Apr 2008 13:12:41 +0000 (GMT)

From: lcaitchison@yahoo.co.uk

Subject: Yahoo! Auto Response

To: noreply@barratthomes.co.uk

MIME-Version: 1.0

Content-Type: text/plain; charset=us-ascii

Message-ID: %26lt;242921.892.qm@web28010.mail.ukl.yahoo.c...

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Spam is sent from my yahoo account via various computers, is the account itself corrupted? Password changed 2xfree anti virus

Anyone can put any address in the FROM and REPLY TO fields without accessing your account. If you are actually seeing them in your SENT folder then someone has access to your account.

鉁?br>Spam is sent from my yahoo account via various computers, is the account itself corrupted? Password changed 2xinternet security software