Hard to say what it exactly pertains to, or rather, which Dll it pertains to.
Some dll which your program uses is either missing/defect, not registered (correctly), or a wrong version on the client machine.
You will need to track the down by trying to find out first, when this exactly happens (what piece of code is being executed at the time the error happens)
Make sure you have VB6 SP 5.
If your program uses ADO, then make sure you are shipping the MDAC along with the installation program.
Also, you need to make sure the db provider is also being inculded, if it is not included automatically by the P&D or included in that version of MDAC which you shipped with your program.
Also, some DLLs/Ocxs need other files top run, which may not be automatically included in your installation for whatever reasons (missing dependency file, or missing references in the dependency file).
Look in the VB directory for a text file called Redist. Look at the files listed for authorized distribution and compare them with the files listed in your VB project under PROJECT|REFERENCES and PROJECT|COMPONENTS.
Any ones not listed, and not included in the MDAC or a db provider file which you are including, are ones which I would look closesly at to see if one of these is causing the problem.
What other references/components are you using not listed in the redist list?
