The Blame Game
The situation you describe is classic finger pointing that exists if and only if users aren't programmers and programmers aren't users. Each blame the other for the problems. Both are wrong. The problem is the process. It's absolutely structural. The person who observes the bug has no power to fix it. Probably users don't even have access to the source code (why this is done in corporate settings where you aren't trying to charge users a fee utterly baffles me). In an open source environment you would have just sent a patch and if the maintainer refused to incorporate it you would simply privately fork (or if it really is a show stopper, you would publicly fork).
I recognize that in a corporate setting your software development business process owner (probably a VP) absolutely can and often does consciously choose to use the inferior model you describe where programmers and users are formally distinct responsibilities. That's life.
Here's some tricks I've learned for coping in the situation you describe:
Document your bug reports carefully, in writing. Ignore any verbal response and report to your manager that development has not formally responded to your bug report. If/When they respond in writing (in email or the tracking system), describe the outcome as "development unable to duplicate". At this point stop talking to the developer other than to tell him that the issue is not resolved. Send your boss a request for help. Explain that the issue is a showstopper and that the developer is not able to duplicate it and is trying to close it without fixing it. Ask for assistance from your manager, and offer to demonstrate the problem to them and to demonstrate that whatever token solution was offered doesn't work for you. From this point on, every chance you get remind your manager that you are at full stop and that you don't know who the owner of the issue is. Always do these kinds of things in writing (email), but with a verbal heads up so your boss reads it. Be calm, cool, and collected about the issue. You are engaged in diplomacy, so act like it. Basically, what you are doing is escalating, articulating, and covering your ass. That's a shitty thing to have to do, but as I said that's life. Also realize that the owner of the process can choose not to solve your problem.
By the way, the reality in most coprorate settings is that users aren't customers. Customers by definition specify both vendor and product. Unless you truly can change these, asking to be treated like a customer is really just symbolism.
Ummm, shrinkwrap "licences" aren't enforcable
With non-free commercial software, there is always a chain of legal contracts connecting the software producer through various intermediaries to the user, thereby theoretically giving the producer control over who can have the software and under what conditions.
You are the kind of hapless fool who believes what the big software companies tell you. Perhpas you should read some of the caselaw:
Most courts that have addressed the validity of the shrinkwrap license have found them to be invalid, characterizing them as contracts of adhesion, unconscionable, and/or unacceptable pursuant to the U.C.C. Step-Saver, 939 F.2d 91; Vault Corp. v. Quaid Software Ltd., 847 F.2d 255 (5th Cir. 1988); Rich, Mass Market Software and the Shrinkwrap License, 23 Colo. Law. 1321.17 A minority of courts have determined that the shrinkwrap license is valid and enforceable. See, ProCD, Inc. v. Zeidenberg, 86 F.3d 1447, 1453 (7th Cir. 1996); Microsoft v. Harmony Computers, 846 F. Supp. 208, 212 (E.D.N.Y. 1994).
This Court holds that transactions making up the distribution chain from Novell through NTC to the end-user are "sales" governed by the U.C.C. Therefore, the first sale doctrine applies. It follows that the purchaser is an "owner" by way of sale and is entitled to the use and enjoyment of the software with the same rights as exist in the purchase of any other good. Said software transactions do not merely constitute the sale of a license to use the software. The shrinkwrap license included with the software is therefore invalid as against such a purchaser insofar as it purports to maintain title to the software in the copyright owner.
Judge Thomas Greene, Novell v. Network Trade Center 25 F. Supp. 2d 1218 (C.D. Utah 1997) (http://bioinformatics.ucsf.edu/bwtaylor/dvd/cases/Novell_v_NTC.html)