In order to help you best please elaborate e bit more:
1. What kind of application are you testing (HTML, Silverlight)?
2. Send us the execution log.
3. Please record a Jing video demonstrating the entire process, so we can better understand what is happening.
4. Provide us with a copy of your test and grant us access to your application so we can reproduce the issue on our end and give you a solution. Is on our demo site something similar to your application?
5. If it is not possible to grant us access to your application, please take a Fiddler trace and attach it to a support ticket in a zip file. You can capture a Fiddler trace using FiddlerCap.
Please confirm that your application allows you to insert two or more identical records. If not, this might cause the problem.
Try to always insert a different text and let me know if you are experiencing the same issue.
Another thing you can try is to set SimulateRealClick (click step which is inserting the test) and SimulateRealTyping (step which is writing the test) to true (see the attached screen shots).
Hope to hear from you soon.
the Telerik team