The version that you are using is from April 2009 and by this time Visual Studio 2010 and 2012 did not exist. Q1 2009 officially support VS2008 and VS2005. You can upgrade your project and use it in VS2010/2012 however, such glitches in design time are possible, since Q1 2009 is not tested with these versions of VS for obvious reasons.
I would suggest that you upgrade your application(s) to our latest version - Q3 2012, which is fully compatible with VS2010 and 2012. Also, the suite has undergone many major improvements, many new controls and features were added for the past three years.
I hope that you find this information useful.
All the best,
the Telerik team