This only occurs if you click in a different textbox. If you use tab or Next, you don't get the error.
If you do use tab or Next, then the correction occurs (unless you hit the "x"), and you don't get an incorrect entry.
Maybe this is an un-addressed jQuery Mobile 1.0.1 problem? I have been using JQM 1.1 and 1.1.1 with Rhodes (and recently moved to 1.2alpha) and haven't seen this problem before. So, perhaps I am only seeing this because I have built a fresh default app and it's using JQM 1.0.1.