It looks like there are a few issues with IOS5 and Filemaker Go.
Hopefully you will get a better answer.
Thank you for your post.
The link provided by Fred Rogers points to the same issue. Our Development and Testing departments are aware of this issue. No additional information is available at this time.
I am having the same problem, btw. I didn't realize there was this great known bug list and posted it in Issue Report.
In case you missed the announcment, FileMaker Go 1.2.4 fixes this issue and is available for download through iTunes.