Hi Luis,
I tried to reproduce this locally, using version 6.3.15, but I was not able to. In order for us to be able to fix this, we need to be able to reproduce so we know what is the problem.
I searched through our reported tracker entries in Gemini, but was not able to find any report that would cover this case, so I can find no indication that it has been fixed in the upcoming version.
For troubleshooting, based on the fact that this seems to be an IE only problem and the fact that you have two different machine, one working and the other one showing the problem, I would suggest that you take a look at IE's security settings and compare between those two machines. I would also suggest that you add your website to the Trusted sites list on both of these machines and lower the security on the Trusted Zone, so that you have common ground to base on.
If that does not help, next step would be to get more information on your application or form. Can you reproduce this on a basic form with just DateTimePicker on the form, with no event handlers registered... just a plain vanilla form ?
Palli