windows 7 64 bit, sysWOW64 failure

The error happens on a windows 7 64 bit, sysWOW64 failure. I have a customer who double clicks on a our xx.cad file that belongs to our software and the application fails to execute randomly. Our application CADRA is a 32 bit application. This is in the event log:

Faulting application name: cadra.exe, version: 0.0.0.0, time stamp: 0x5101f00f

Faulting module name: ntdll.dll, version: 6.1.7601.17725, time stamp: 0x4ec49b8f

Exception code: 0xc0000005

Fault offset: 0x0002e17a

Faulting process id: 0x18c8

Faulting application start time: 0x01ce62bf8cb0d8de

Faulting application path: C:\CADRA\cadra.exe

Faulting module path: C:\windows\SysWOW64\ntdll.dll

Report Id: ce13ba31-ceb2-11e2-a6e8-8851fbcb6780

Any clues as to what I can check to make this stop failing is appreciated.