First off, one thing: once your script is saved to Google Drive, every single letter you type is saved, in many cases several times per second. It isn't just happening if and when you see this "Saving..." notification.
This message means that the Google Drive code is developing a backlog that it hasn't managed to transfer to the cloud yet. After 1 - 2 minutes, YouMeScript cuts off more work, so you don't get in a situation where you're working away thinking all's good, close the tab, and lose your unsaved work.
In the vast majority of cases this happens when the internet connection gets flaky or dies. YouMeScript makes roughly the same demands on your internet as Docs does, so that can be a good way to test that all is okay, and is definitely the first thing to try.
HOWEVER, I have now seen a few cases where this was happening even on a rock-solid connection, and in that case there may be something screwy with the way Google's servers are handling that particular script.
SO, start an entirely new script, and copy and paste your work from one to the other, then of course SAVE the new script, and continue working in that. If this advice helps you out, I'd be really grateful to hear about it, either here or via email: support@youmescript.com
Thanks folks.
- Jake