Yes, you can attach your VI. In some cases it may be more convenient to post a "snippet" - a PNG image with embedded LabVIEW code - which you can create by selecting all or a portion of the block diagram, then selecting Create Snippet from the Edit menu. That allows a forum user to see your code without opening LabVIEW (or if they don't have at least as new a version as you), but doesn't work well when there are subVIs.
Did you have any luck finding the problem?
It's easier to chain the error wires than merge them (the error out from one node connects to the error in of the following node). This is also a common way to dictate execution order in LabVIEW. Most (but not all) functions that accept an error input do nothing when an error is present on the input; the exceptions are generally functions that you would want to execute even if there's an error, such as functions that dispose of resources.
That said, were you able to solve the problem? If not, can you put a debugger on the .NET assembly while it's being called from LabVIEW? Can you share your LabVIEW code? Do you have working example code in another language that we can compare to your LabVIEW code?