This sounds like a problem with the version of Java you’re using, and there is a setting specifically for what version of java the mobile module uses. You can find it in the Ignition Gateway in the Configure section under Mobile -> Settings. You should make sure that the Java Path is set to something like ‘C:\Program Files\Java\jre7\bin\java.exe’
If that’s set to the correct path, then you can try clearing the Java cache on the computer Ignition is installed on.