Application has stopped working - bug?

Application has stopped working - bug?

Hi, without me making changes to it, one of my applications has stopped working. When I try to view the form for my Transactions app, it will not appear, and so I cannot add new data to my app.

One strange thing is that when I duplicate the application, the new copy will work straight away.

When I click Add in my Transactions View, I get the following alert:

"400: Invalid path /jsp/themes/common/form/form was requested"
pipedreambomb