Trouble setting custom weather in v5?

[mtr75 653]

First flight back in v5 since September, and for whatever reason I can't set custom weather. I went to enter a cloud layer, and when I type in a number in the first box for the bottoms and then click the next box to put in the tops, the first box reverts right back to 0. It will let me set a cloud layer from 0 to 1 feet, but that's not very realistic for IFR flight!

Any ideas? Sim is fully updated to 5.1.

Thanks!