This happens on my wife's computer;
When she either reads or just deletes any email without reading, "the problem" causes the remaining emails to move up or down without changing their headers (tilte of e-mail) and when she attempts to read the next e-mail the headers will display incorrectly on the wrong email. This causes desired e-mails to be deleted because they display the wrong header/title of a previous deleted e-mail.
She can exit out and log back in and it will sometimes fix the problem, but not always.
I have checked her e-mail settings and they are indentical to mine, (I do not have this problem with my e-mail).
We both use Windows 7 64 bit, Web browser Firefox.
A little assistance please..