Vaadin 6.2.7 default theme seems to get somewhat mixed up with IE 8.0.6001.18702 especially around borders. I am a bit in a hurry so do no thave time to send screenshots right now. I will also test at home to see if this is just some glitch with this computer. There is some similar graphical minor errors in vaadin site as well.
At home I have IE 8.0.6001.18904 which is working perfectly. I am unable say whether this is IE minor version specific bug or if the other machine is in someway mixed up.