Many of the available test tools use similar mechanisms to deal with custom controls. Knowing which you have already tried would save folks from recommending other tools likely to have the same problems.
Telerik will always be an issue to automate unless they work with the manufacturer of specific tools to make their controls compatible. Maybe they don't want to be compatible with other test tools so they can sell their own tool? Don't know...
Like anyone else, you're on your own.
I had a lot of success with QAWizard Pro from Seapine. On my last project we used Telerik extensively and I worked with the Seapine Engineers to get the their tool working well with them.. There's an eval download you could try for free if you want. The only issuess I had were with the Telerik Grids. They were difficult to analyze but were readable. Our developers had to hack the controls to get them to do what we wanted though. I believe Telerik has a tool to work with their controls. You might investigate that too.
Success is the ability to go from one failure to another with no loss of enthusiasm.
~ Winston Churchill ~
You may want to try our tool, Eggplant. By taking a visual approach to testing, Eggplant is able to easily work with custom and non-standard controls on any platform. So it doesn't matter what underlying technology was used to create a web or desktop application -- it's all the same to us.
Doug Simons, Principal Developer
TestPlant, makers of eggPlant, the Cross-Platform GUI Testing Tool http://www.testplant.com