Recently, we had a similar problem with RadGridView, which entered infinite layout cycle. It was reproducible when UI Virtualization is disabled and row count is larger than ~150, but we fixed it as soon as it was reported. Can you please confirm which version you are using? If you experience this erroneous behavior even with the latest version, it will be great if you can send us a sample project to debug.
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.