I am building an app that uses a tabbed UI which contains many tabs and pop windows with detailed information on a record. On my home machine, whenever I select preview in default browser from the the tool bar I get the following error.
500 Internal Server Error

Script Error
Error:Script:" /LivePreview/ClientInfoSheet_PageLayoutLivePreview.a5w" line:31
x_out = a5_ajax_PageLayout(tmpl)
Property not found
tmpl.precalc.PageLayoutMasterTemplate subelement not found.

1. The error does not occur on my laptop.
2. I use the dropbox for the development files so they are always identical.
3. I have tried brand new Ux's with no connection to the UI and get the same error.
3. The pages render properly under live preview, in the browser when selected from live preview, when viewed inside the tabbed UI and when published.

Still workable by previewing through the tabbed UI but it is annoying when working a layout where you are constantly checking to see how a 25px change looks.

Any thoughts?