Yes Sai, that is what I am trying to say...
The WEVER is a version related field.... it has its own domain level constraints that the value range should be 1,2,3 ... You cannot use X there .. since you used that field as Check box, the system tries to allocate X to that field and hence you are getting the domain level error saying 'Please enter valid value'..
Since you are already having the dropdown for it, why to use Check box again (to me it seems redundant)...
If you still want to use the checkbox, then remove the link to data dictionary on that field...
Regards,
Venkat