I've been trying to save up gems for a sonic appliance, but when I'm low on coins and try to buy something, the "Oh Darn! You don't have enough coins." window pop up.
There's an OK button and an X button, right? The OK button should direct you to another window with three buttons -- Convert Gems, Buy more gems, and X.
When I pressed OK, it automatically converts the remaining gems I've been saving up to x coins.
It's very annoying, since I've made two conversions already.