Thank you for your post.
What version of FileMaker Pro are you using? What version of FileMaker Go are you using?
If you create a new file in FileMaker Pro with one field, set it for Network Sharing, and then access the file from FileMaker Go, are you able to create a record and update it?
What other applications do you have open?
If you relaunch FileMaker Go and access the file, does it then update correctly?
If you reboot the iPad, launch FileMaker Go and access the file, does it update correctly?
Any other information you can provide may be helpful.
I have reported this same issue on my iPhone 4S. For me restarting the FM GO App, didn't have to restart the whole device, cleared the issue. I suspect that this is another symptom of this issue I reported here: GetField returns null in FileMaker Go
In that thread, I've posted a script that can detect this issue and warn the user to restart the app.