TestComplete working with a very large application loses the ability to access application internal

I work with automated testing of a very large Delphi XE application using TestComplete 9. The application has a 180MB executable. The automation environment is Windows XP, 32 bit.

TestComplete is unable to access public, protected or private properties. Published properties may or may not be accessible - there doesn't seem to be any pattern to whether or not a given published property can be accessed. All methods are usually accessible, but may be unavailable, again without any observable pattern. The automation codebase has not changed.

Initially, I observed occasional instances where form information that should have been available to TestComplete wasn't present. The same automation could be rerun against the same executable and access the information without errors: the pattern of failure appeared to be random and was never solved.

Now, not only does TestComplete working with the large application fail to access properties and methods necessary for the automation to complete, when TestComplete attempts to access the information it will often cause the application to fail with no further information. This behavior can be reproduced with the application at will, but can't be built into a test application.

The application has been under more or less continuous development for about 25 years, and still includes some of the original DOS TurboPascal procedural code, so the internal workings of the application are very complex.

Can anyone point me to any resources or suggestions for getting the automation running again? At present there is maybe 3 hours (of 60) automated regression being performed due to the problems with accessing application internal information.