Ok, I think I have figured out the steps to reproduce.
Create a new project
create designer file. Name it with UpperCase
load it in the activity
The interesting thing I found was that when I added a layout file using "add file", it seemed to work just fine. Upon further testing while writing this, I realized that when using "add file", it renames the "bal" file within the OS with all lowercase but seems to maintain the upper case format within the IDE. I'm using win7.
P.S. Upon further investigation, the test attached won't do much good because the "export to ZIP" process seems to rename the "bal" file all lowercase. Basically it seems to me the designer is supposed to save the file all lowercase (while maintaining the format within the IDE) but it isn't.
P.P.S. and this would appear to be the same issue/cause in b4i as noted above.