We are not aware of the mentioned issue. I can suggest that you try the following steps:
- Remove all of the custom CSS to see whether this resolve the issue. If that is so you can start turning piece by piece the styles until you find and fix the problematic rules.
- Try to upgrade to latest Telerik UI version - currently this is 2014.1.401.
If the above steps do not help we would need a fully runnable sample that reproduces the issue, so we can make a further investigation on the matter.