Yes, me too. I put on and off the Quivers of Infinity, Elements and Fire and tested it first on Ice Fiends and then on Ogre Lords. The problem is that the resistances are random so you can't really say for sure what made the difference. But I did it for quite some time and I would validate what Frarc found out: Not applicable to melee damage. "Of course", you could say "it's a Quiver!". Not that easy because the 5% DCI of the Quiver of Infinity DOES count on a Melee.
I think this is an interesting question for FoF. I checked them since March 2006. There were two question about the damage type of Quivers but only related to Archery. I searched the Knowlegde base too without results.
Additionally to your question you could also ask if the equipped Quiver overrides the damage type of the melee weapon like it does on a bow. (Obviously not but I would like to read the explanation resp. the verification for this as well.)
I would have sent it in already but the feedback site is not encrypted and I refuse to sent sensitive data like my account name this way. (I'm kind of a chicken in this regard
)