There seems to be an issue with creating plain text files in v1.4.0.64. The environment is as follows:
Alfresco Community 4.2.b on Centos 6.3 x64
Alfresco Mobile 1.4 on iOS 6.0.1
Creating a plain text file in version 1.4.0.64 causes the application to send you back to the phone's home screen. The app is still listed in the multitasking list, but in Diagnostics & Usage its logged as a crash. The application does still write the file to the server, and it can be edited after reopening the application. It can also be edited on the server.