Hello, Nathan,
I've got 2 crash reports from you today. We will release a PhotoScan update today, which includes the fixes to the problems you have reported. I hope it would not crash any more, or at least not so often =)
I'll post one more message in this thread once the update is ready for download.
As for the "Can't build model" error, it is often caused by insufficient memory problem, especially on the 32 bit OS. But it should not happen for small photo sets, like 4 photos.
I will be happy to help you with this problem, but I need the photos you are processing to reproduce it.
With best regards,
Dmitry Semyonov
AgiSoft LLC