In Yosemite, Magic Mouse double-click function doesn't work

On my iMac running Yosemite 10.10.2, the double-click function on the Magic Mouse no longer works. So to open a folder, or anything for that matter, I must always do click-control ---and that doesn't work for everything. For example, I can't double click on a character in Glyphs, so this renders Glyphs useless. And so on... I have gone into preferences to see if anything was amiss in the settings, but everything checked out fine. Is there a fix for this, or do I have to wait for the next upgrade for Yosemite? Help! Thanks... --Royce