I've been examining the history of currencies. I think the practice of devaluing the Roman currency was started by Nero, and continued by following emperors. I'm aware that the decline and fall of the Empire is a complicated subject with many explanations, but I'm not familiar with any publications/ historians that focus on the currency as a factor. Thanks!
Relatedly, devaluing the denarius would cause falling real wages (especially among people with fixed salaries, so occupations like soldiers would be particularly affected - looting notwithstanding) and inflation, so if anyone has any evidence that those symptoms contributed to the fall, then they would help answer OP's question
There is an interesting little episode that is mostly relevant in economic history and not crucial for the decline of the Roman economy, but it highlights the problem in a nutshell: Diocletians "edict on prices".
Although Aurelian deserves most of the credit for salvaging the empire from the crisis of the third century, Diocletian was the emperor who broke the circle of usurpations and returned some long term stability. While he was one of the Illyrian generals, a soldier emperor like so many had come before him, Diocletian did not die by the sword. He reigned for decades instead of months, then retired to his cabbage farm (literally!), and died peacefully in his bed. Though successfull in most endeavors, the one thing he never got right was fixing the ecenomy.
The empire had suffered from decades of warfare, some against the Persians, but mostly among itself. By this time, the Roman farmer soldier who had to fulfill wealth requirements and bring his own gear was ancient history. Since the marian reforms, soldiers were paid professionals, mostly poor people from the border provinces in it for the money. And unlike the earlier campaings of conquest, civil wars don't generate much loot.
As previous emperors had found out (hello Galba), not paying your soldiers what they feel they were owed when you come to power ahead of the army is not a sustainable policy. So, the obvious solution was to reduce the silver content of the denarius to be able to make more of them.
This inflation, a concept that the Romans didn't seem to fully grasp at the time, caused buying power of wages of average laborers to drop off a cliff. Ever more people in the capital became dependent on the grain dole to feed themselves and the soldiers got itchy. Diocletian recognized the worthlessness of the coins as the root of the problem and started a program to increase the silver content again.
What he didn't understand is that the worthlessness of the coins was not caused by the lack of silver, but by their number. While he gave out the new higher silver content coins, he critically failed to recall the old cut coins in sufficient number. Prices continued to rise, leaving Diocletian baffled.
To put and end to this escalating crisis, he decided that henceforth every good should have a maximum price attached to it. The imperial beurocracy created an exhaustive list of every conceivable trade and attached to it a price that seemed fair. For example:
On and on it goes, pages upon pages, published on stones and, in modern times, google books: http://books.google.de/books?id=EZg0VBWfs-wC . What happens when you demand a higher price? Death.
At least in theory. In practice the black market was soon out of control and the whole project died a quiet death and was quickly swept under the rug. Diocletian, thoug, still had the problem of paying his soldiers, and the damn coins were just no good. In the end soldiers were paid directly by their quartermasters in goods.
This solution was also applied to the matching problem that tax revenue in coins was worthless. The whole tax system was reorganized by a similar list of the value of goods when used to pay taxes. You (as in you, a city) owed 4 million units of tax, payable in 20 million ducks, 400 million cauliflower or 500 years of wall painting service, in whatever combination you could most conveniently provide. Diocletian also forbid changing your trade and made it hereditary. When your grandfather under Diocletian happened to be a stone mason, you had to be a stone mason as well, whether you liked that or not. This is essentially a kind of early guild system or a trade caste system if you will.
All in all, I would say, if the devaluation of coins did not contribute to the decline of the Roman empire, Diocletian's economic policies sure as hell did their part. I would love to pin the entire malaise on him, because it is such a nice and simple story, but the time frame just seems too long and the solidus was created soon after his death and maintained its value for more than 500 years. On the other hand, restricting free choice of profession has obviously a long delay until starts to show effects (by the way, does anybod know when this policy ended?). It also doesn't explain why the east survived.
In any case, it is very notable that the western empire fell without ever suffering a military defeat on anything resembling the scale of Cannae. The stubborn resurgence that characterized the republic and early empire, the ability quickly raise huge armies or navies after crushing defeats, was gone after the death of Julian. There must have been reasons for this change.