This just started happening today. I entered a custom mnemonic, and click save. Screen goes back to word screen and my mnemonic shows up. If I go to the next word (right arrow at top) and then go back (left arrow), skritter says "no mnemonic created yet." But if you open up the mnemonic screen, my mnemonic is still there in the text entry box.
This is happening with all new entered mnemonics as of now. I have tried logging off and logging back in. Win 7 64 bit.

Does it still show up the next time you study the word? Like if you edit the mnemonic then immediately refresh the screen?