Minimize and Max. stopped working.

This started within the last week. I tried restarting without add-ons but it did not help. When I used to click the Minimize boxes in upper right corner, the address book or emails would become smaller and I could drag the corner to create a custom size. Now, when I click the Min button, I do not see any difference in size. If I try to drag the upper right area to resize the wondow /a custom size the complete window starts to become smaller ut seems to be locked or anchored in the upper right. The same thing happens on all T Bird boxes that have min and max buttons in the upper right corner. The only way to return to the normal size is to close TB completely and reopen it.