In a application getting this error, but application still works, each 2-3 times changing scene getting same errors.

2012-01-26 21:10:39.809 java[355:407] *** Assertion failure in -[NSEvent userData], /SourceCache/AppKit/AppKit-1138.23/AppKit.subproj/NSEvent.m:2071
2012-01-26 21:10:39.810 java[355:407] Invalid message sent to event "NSEvent: type=LMouseDown loc=(177,251) time=2844.5 flags=0x100 win=0x7fd80143c040 winNum=134 ctxt=0x0 evNum=426 click=1 buttonNumber=0 pressure=1"
2012-01-26 21:10:39.856 java[355:407] (
0 CoreFoundation 0x00007fff8ef4d286 __exceptionPreprocess + 198
1 libobjc.A.dylib 0x00007fff98871d5e objc_exception_throw + 43
2 CoreFoundation 0x00007fff8ef4d0ba +[NSException raise:format:arguments:] + 106
3 Foundation 0x00007fff965b67d3 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 169
4 AppKit 0x00007fff98e982c0 -[NSEvent userData] + 292
5 libmat.jnilib 0x00000001239164ca -[GlassViewDelegate sendJavaMouseEvent:type:button:] + 836
6 libmat.jnilib 0x0000000123916540 -[GlassViewDelegate sendJavaMouseEvent:type:button:] + 954
7 AppKit 0x00007fff98e190e0 -[NSWindow sendEvent:] + 6306
8 libmat.jnilib 0x0000000123918417 -[GlassWindow sendEvent:] + 298
9 AppKit 0x00007fff98db168f -[NSApplication sendEvent:] + 5593
10 AppKit 0x00007fff98d47682 -[NSApplication run] + 555
11 libmat.jnilib 0x0000000123904dd5 -[GlassApplication runLoop:] + 1715
12 CoreFoundation 0x00007fff8ef3ca1d -[NSObject performSelector:withObject:] + 61
13 Foundation 0x00007fff9653ae44 __NSThreadPerformPerform + 214
14 CoreFoundation 0x00007fff8eebbb51 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
15 CoreFoundation 0x00007fff8eebb3bd __CFRunLoopDoSources0 + 253
16 CoreFoundation 0x00007fff8eee21a9 __CFRunLoopRun + 905
17 CoreFoundation 0x00007fff8eee1ae6 CFRunLoopRunSpecific + 230
18 java 0x000000010975e843 java + 18499
19 java 0x000000010975e29a java + 17050
20 java 0x000000010975ba98 java + 6808
     ??? 0x0000000000000004 0x0 + 4
)
2012-01-26 21:10:39.925 java[355:407] *** Assertion failure in -[NSEvent userData], /SourceCache/AppKit/AppKit-1138.23/AppKit.subproj/NSEvent.m:2071
2012-01-26 21:10:39.925 java[355:407] Invalid message sent to event "NSEvent: type=LMouseUp loc=(177,251) time=2844.6 flags=0x100 win=0x7fd80143c040 winNum=134 ctxt=0x0 evNum=426 click=1 buttonNumber=0 pressure=0"
2012-01-26 21:10:39.926 java[355:407] (
0 CoreFoundation 0x00007fff8ef4d286 __exceptionPreprocess + 198
1 libobjc.A.dylib 0x00007fff98871d5e objc_exception_throw + 43
2 CoreFoundation 0x00007fff8ef4d0ba +[NSException raise:format:arguments:] + 106
3 Foundation 0x00007fff965b67d3 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:] + 169
4 AppKit 0x00007fff98e982c0 -[NSEvent userData] + 292
5 libmat.jnilib 0x00000001239164ca -[GlassViewDelegate sendJavaMouseEvent:type:button:] + 836
6 libmat.jnilib 0x0000000123916540 -[GlassViewDelegate sendJavaMouseEvent:type:button:] + 954
7 AppKit 0x00007fff98e191a6 -[NSWindow sendEvent:] + 6504
8 libmat.jnilib 0x0000000123918417 -[GlassWindow sendEvent:] + 298
9 AppKit 0x00007fff98db168f -[NSApplication sendEvent:] + 5593
10 AppKit 0x00007fff98d47682 -[NSApplication run] + 555
11 libmat.jnilib 0x0000000123904dd5 -[GlassApplication runLoop:] + 1715
12 CoreFoundation 0x00007fff8ef3ca1d -[NSObject performSelector:withObject:] + 61
13 Foundation 0x00007fff9653ae44 __NSThreadPerformPerform + 214
14 CoreFoundation 0x00007fff8eebbb51 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
15 CoreFoundation 0x00007fff8eebb3bd __CFRunLoopDoSources0 + 253
16 CoreFoundation 0x00007fff8eee21a9 __CFRunLoopRun + 905
17 CoreFoundation 0x00007fff8eee1ae6 CFRunLoopRunSpecific + 230
18 java 0x000000010975e843 java + 18499
19 java 0x000000010975e29a java + 17050
20 java 0x000000010975ba98 java + 6808
     ??? 0x0000000000000004 0x0 + 4
)