Justin,
I am curious if this customization was applied prior to SL 7.0 and was inherited with an upgrade to 7.0 or if it was a new customization done under 7.0. Do those screens open just fine with your customizations in place and the issue only happens if you go into customization mode again and try to drag the new fields? At least that is the way I am reading what you are saying.
If the customizations were done with Customization Manager you should be able to enter customization mode and select remove changes to take these out and start over again. I realize this is a bit of a harsh approach.
As a last resort, you can delete the customization and start over again by executing the following SQL command against your system database:
delete from customvba where screened = 'nnnnnnn'
substitute the screen id shown in the header of the offending screen for the nnnnnnn in the above command.
I have not tried to customize those screens under 7.0 but I have customized various AR screens and cannot reproduce your problem with those screens.