Hello Patrik,
Thank you for contacting us on this issue.
Unfortunately, I was not able to reproduce the described behavior (with binaries from 2012_2_1009_DEV_hotfix). However, I might be missing an important part of your implementation. This is why I've attached the test project I used to reproduce the issue - please take a look at it and feel free to modify it in order to show us how to reproduce the described behavior of the RadHtmlPlaceholder.
Regards,
Milena
Telerik
Check out Telerik Analytics, the service which allows developers to discover app usage patterns, analyze user data, log exceptions, solve problems and profile application performance at run time.
Watch the videos and start improving your app based on facts, not hunches.