BB Bold 9000 :: Yahoo Mail - Deleting Mail From Phone Delete It From Computer

This is really bothering me.I have a yahoo mail account set up on my phone - It has been on there for over a year - it has always worked this way - If I get an email (the phone goes "bing") and i read it on the computer - and responded and delete it on the computer it would be removed from the phone the next time i looked. Recently I began noticing that the message is not being delated from the phone if I delete it from the mailbox, and I can't figure out why.

Basically I want to be able to read the message on the computer and hit delete and for it do the same thing on my blackberry and vise versa. Now it seems to work if I delete the message on the BB then it will not be in the Mailbox on the computer.