Hello Sean O'Dea,
I managed to reproduce the problem. Currently we are refactoring some of the code of RadNumericUpDown that will fix this issue and some others. We will do our best to be ready for SP1 which is scheduled for the second week of December. However if we don't manage to finish on time and test the changes, this fix would be included in the first Weekly Build after the SP1. Hope this time frame is acceptable for you.
Please, excuse us for the inconvenience. We have added points to your account for the report. Don't hesitate to contact us if you have other questions.
the Telerik team