PDB files with source code linkage

[sludgenz]

We've been having a great deal of problems getting our pdb files
linking back to our source files when doing post-mortem debugging.
I know this is possible because I've seen it done. At the moment we
have our clients install Dr Watson and set it to generate a full dump
file. When a crash is reported we take the dump file and put it in the
same directory as our .pdb files and open the dump file with Visual
Studio .NET. We then press play and we get a stack with all the
function symbols but only disassembly windows when we try to go to one
of our functions.
Now in some of our over branches (some of which aren't very different)
the .pdb files will actually link back to source files. If we use a hex
editor to examine the difference between the .pdb files we can see that
those which allow you to link back to source have all the paths to our
..c and .cpp files whereas those that don't only have the paths to our
..obj files.
We've checked all the project settings for our .dll projects and cannot
find any significant difference between those source base which produce
source code linked .pdb files and those that don't.
Anyone have any ideas?