X-Cart forums - Weird problem when editing Fast Lane Checkout

I have version 4.0.13 in my signature, but these problems are with 4.1.3 (as I am getting it installed/configured for an upgrade)

I've got this weeeird problem I need help understanding why its doing, and how to avoid or whatever..

I'm trying to customize the Fast Lane Checkout (mostly just visual/aesthetic changes). Any time I make a single change (I can change just the value of a CSS property) and it breaks the Fast Lane Checkout...

By breaks, I mean that when I save the change and refresh, the Titles disappear from the dialog boxes, and the right hand side box (that details "Want to register now..") disappears.. just the login box on the left remains with information, although the title is missing.

It gets even a little weirder.. if I change whatever I changed back (and I'm not even joking, I just changed the style='display:none;' value that it spits out based on an if statement (to display the registraiton form, when its hidden at first)... I changed "display" to "disploy" to purposely break the CSS from hiding the registration box, and these weird happenings occured.. I then immediately put it back to display (just did undo) and resaved, and its still broken..

I can fix it by making a backup copy of skin1/, then doing a full recursive and overwrite copy of skin1_originals/ to skin1, then doing another recursive overwriting copy from the skin1 backup I made to skin1, and viola.. its fixed.. which I find odd, considering the last step (overwriting skin1 with the backup) overwrites the middle step that fixes it..

Anyone that can help make sense of this, it will be greatly appreciated. Thank you.