I face a similar issue that is been reported in the below thread.
(Column header getting detached when resized)
finally the thread ends up with updated in SVN.
I followed the below steps to build the ext for fixing the above issue:
Step 1 : http://code.extjs.com/svn/ext/branches/ext2.0
Step 2 : Supplied required credentials
Step 3 : Downloaded ext.jsb, examples.jsb, resources.jsb
Step 4 : Replaced above 3 files in my ext folder (ext.jsb in C:\ext\source, resources.jsb in C:\ext\resources and examples.jsb in C:\ext\examples)
Step 5 : Using JSBuilder i built ext folder in C:\newext
The updated extjs (in newext) edit-grid example still has the column detachment issue.
Please guide me or correct me if i am doing some thing wrong!