Please go through the following troubleshooting steps:
- Make sure the ROM is in .n64, .v64, .z64, or .zip format (extensions .7z, .tar, and .gz are not supported and must be unzipped)
- If the ROM is in .zip format, try unzipping it on your computer to make sure the file isn't corrupt
- If the ROM is in .zip format, make sure the compressed file inside it has the extension .n64, .v64, or .z64
- Try other games, or try getting the ROMs from another source
If those don't fix your problem, then perform the following steps:
1) Backup your saves (in the folder [sdcard]/Android/data/paulscode.android.mupen64plus[.xperiaplay]/data/save)
2) Select the "Restore App Data" option under the "Settings" menu.
3) If your games start working again, then restore the saves you backed up in step 1.
If that doesn't fix your problem, then install the free app "Android System Info" from the Android Market. Run it and look up your supported OpenGL versions under the "System" tab. If version 2.0 is not listed, then your device does not support GLES2, which is currently a requirement for the emulator to work. I plan to develop a video plug-in for version 1.1 in the future, but it will probably be some time before it is ready.
If none of the above things are the cause of your problem, then install and run the following test app once:
Verbose Test App
Then install the free app "aLogcat" from the Android Market. Run aLogcat, and wait for it to read the logs (may take several minutes the first time you run it, so be patient). When it is finished reading the logs, then select "Clear" from the menu, and close aLogcat. Run the test app again, and get it to crash by opening one of the games. Then run aLogcat again, and this time choose "Save" from the menu. It will save a text file to your SD Card under the folder "alogcat". Please post that here so I can read through it to see if there is any useful information on what might be causing the problem.