Debug - Unmanaged and managed code

Hi,

I am facing a problem with a legacy application a part of which is being
ported to VS 2005.

I have a VB exe 'A.Exe' (legacy code) calling methods from a C-Sharp dll
say, 'C.dll', which in turn calls into other dlls and Exes. Can I debug the
code of 'A.Exe' and 'C.dll'?

I tried the following:
1. Copy A.Exe into the bin/Debug folder of 'C.dll'
2. In the Project Properties of 'C.dll', Debug Tab:
- Check "Enable unmanaged code debugging".
- Select "Start External Program". Specified the path of 'A.Exe' that is
placed under bin/Debug of 'C.dll'.

In the above scenario, I am able to debug 'C.dll' and the other dlls and
Exes that is called by it. Then I get an error Messagebox from Visual Studio
stating
"Windows has triggered a breakpoint in 'A.Exe'. This may be due to a
corruption of the heap, and indicates a bug in 'A.Exe' or any of the DLLs it
has loaded."
When I click on 'Break', the disassembly of 'A.Exe' is shown. In order to
debug the problem, I would like to get into the code of 'A.Exe'.
But don't know how that can be done.

For "Start External Program" in the 'Debug' tab, I also tried giving the
path of A.Exe as the folder that has the code for 'A.exe' and the
corresponding executable. In this case too, I am unable to debug the code.

Any way out?