it's not related to mods - it has to do something with styles.
yes... on 95,84% it's caused by styles with fixed width. + attribut size in input elements
currently, the fastest fix which i found, is add this to style/imports/base_admin.css:
#adminconsole td input {width: 100%;}
it solves the overflow, but it has a lot of side effects.
i've tested this just with Zoey B&W style, but it should works with others... so try it.
btw, coxis, what style do you use?
iam afraid that a complete solution will need some deeper modifications. let's find out what...