App Close : Crash

Since 3.1.3.GA, my app has been throwing the following crash error:

Sep 23 13:12:24 DZ-Mark-V Zypher[3455] <Warning>: [ERROR] The application has crashed with an uncaught exception 'org.zypher.TiUITabProxy'.
    Reason:
    Invalid type passed to function
    Stack trace:
 
    0   CoreFoundation                      0x31153e8b <redacted> + 130
    1   libobjc.A.dylib                     0x3b44d6c7 objc_exception_throw + 38
    2   Zypher                              0x0018a8ad Zypher + 608429
    3   Zypher                              0x00149ec1 Zypher + 343745
    4   Zypher                              0x0014a2a5 Zypher + 344741
    5   Zypher                              0x0018b0e1 Zypher + 610529
    6   Zypher                              0x0018addb Zypher + 609755
    7   Zypher                              0x0014a99f Zypher + 346527
    8   Zypher                              0x001ecaf1 Zypher + 1010417
    9   Zypher                              0x0018b0e1 Zypher + 610529
    10  Zypher                              0x0018b367 Zypher + 611175
    11  Zypher                              0x001d4983 Zypher + 911747
    12  UIKit                               0x339609f5 <redacted> + 152
    13  UIKit                               0x3395ddf7 <redacted> + 2474
    14  UIKit                               0x338de2a7 <redacted> + 774
    15  UIKit                               0x338ddedd <redacted> + 72
    16  UIKit                               0x33943ca1 <redacted> + 664
    17  GraphicsServices                    0x35dbf76d <redacted> + 608
    18  GraphicsServices                    0x35dbf357 <redacted> + 34
    19  CoreFoundation                      0x3111e77f <redacted> + 34
    20  CoreFoundation                      0x3111e71b <redacted> + 346
    21  CoreFoundation                      0x3111cee7 <redacted> + 1406
    22  CoreFoundation                      0x31087541 CFRunLoopRunSpecific + 524
    23  CoreFoundation                      0x31087323 CFRunLoopRunInMode + 106
    24  GraphicsServices                    0x35dbe2eb GSEventRunModal + 138
    25  UIKit                               0x3393e1e5 UIApplicationMain + 1136
    26  Zypher                              0x000fbc23 Zypher + 23587
    27  libdyld.dylib                       0x3b946ab7 <redacted> + 2
Sep 23 13:12:24 DZ-Mark-V Zypher[3455] <Error>: *** Terminating app due to uncaught exception 'org.zypher.TiUITabProxy', reason: 'Invalid type passed to function'
    *** First throw call stack:
    (0x31153e8b 0x3b44d6c7 0x18a8ad 0x149ec1 0x14a2a5 0x18b0e1 0x18addb 0x14a99f 0x1ecaf1 0x18b0e1 0x18b367 0x1d4983 0x339609f5 0x3395ddf7 0x338de2a7 0x338ddedd 0x33943ca1 0x35dbf76d 0x35dbf357 0x3111e77f 0x3111e71b 0x3111cee7 0x31087541 0x31087323 0x35dbe2eb 0x3393e1e5 0xfbc23 0x3b946ab7)
Sep 23 13:12:24 DZ-Mark-V ReportCrash[3456] <Notice>: ReportCrash acting against PID 3455
Sep 23 13:12:25 DZ-Mark-V ReportCrash[3456] <Notice>: Formulating crash report for process Zypher[3455]
Sep 23 13:12:25 DZ-Mark-V com.apple.launchd[1] (UIKitApplication:com.dezinezync.stacks[0x808f][3455]) <Warning>: (UIKitApplication:com.dezinezync.stacks[0x808f]) Job appears to have crashed: Abort trap: 6
Sep 23 13:12:25 DZ-Mark-V backboardd[28] <Warning>: Application 'UIKitApplication:com.dezinezync.stacks[0x808f]' quit with signal 6: Abort trap: 6

This happens when I invoke the multi-tasking tray, and dismiss the app to close it.

Here's the non-redacted version (crash report): http://cl.ly/code/0F0r043B2Z2x

Here's my tabGroup code

ui.makeTabGroup = function() {
    return Ti.UI.createTabGroup({
        width: Ti.UI.FILL,
        height: Ti.UI.FILL,
        backgroundColor: ui.backgroundColor,
        borderRadius: 0,
        tintColor: ui.accentColor
    });
}
 
// var ui is one of my globals

The only event attached to my tabgroup is the open event where I register the device for Push Notifications. I can't seem to figure out what could be causing this. Any help would be appreciated.