I noticed the following lines in the release notes for 2010.2.929:
Fixed: The dropdown size is incorrect the first time the dropdown opens if its height exceeds the window's visible height and the document has 'overflow: hidden'
Fixed: The dropdown size is incorrect in IE the first time if there are items with long text with spaces
However, we're now seeing a similar problem (the dropdown size is very small the first time you open it; it's correctly sized the second and subsequent times) in our application after upgrading to 2010.2.929; we weren't seeing it before (on the Q2 SP1 release). It appears to occur on a RadComboBox that has items with long text with spaces; the dropdown size isn't longer than the window size.
Is there a workaround/known issue?