Just a word to say you are not alone. The problem has been around since version 2.0. Workaround: Create a new empty database; import all your objects into it; and everything should be functional again...
Good Luck!
JR
Can anyone help in recommending the best way to adapt a Goodman ARUF30 air handler to existing duct work from an oil fired furnace? The Return Side hood is 20"x20" on the furnace but only 10"x20" at the joist level. The heat side is 21"x20" on the furnace with the same at the joist level...