Hello,
We have such an issue logged into our system as a bug report. You can vote for it and follow its progress on the Feedback Portal here:
TreeListView with 700 columns does not display grid lines.
I apologize for the inconvenience.
Regards,
Didie
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.