C++ DLL called from C#

I am debugging a DLL written in C++, the DLL is loaded by a C# application using COM.

I am seeing a number of

     0xC0000005: Access violation reading location 0x00000000.

Messages in the Output panel in the debugger, many of these occur before the DLL is loaded and if I break on any one of these the call stack shows an address:

    058fd5e3()
    mscorlib.ni.dll!7146608d()
    [Frames below may be incorrect and/or missing, no symbols loaded for mscorlib.ni.dll]

And much more similar messages. Is this anything to be concerned about? How can I go about finding out what is causing this?

Yes, this is a reason for concern. The error message is from a null pointer access, which is Undefined Behavior in C++. Undefined Behavior can and has erased hard disks.

You need the code and the PDB file to debug this. Your comment suggests there is some political wrangling. In that case, dump the DLL. The error message is sufficiently bad that you should assume a disaster is waiting to happen. The fact that the source code is intentionally missing only amplifies that risk analysis.