Here's a message to whomever over at Bethesda keeps tabs on these forums and the complaints from customers about bugs and glitches...

Here it is:

I'm a new forum subscriber but long time lurker, and the bug/glitch where Merchant's inventories won't restock and as well as the bug/glitch where Merchants continuously hang on to EVERYTHING you sell them (you should be able to imagine the lag and other problems which that causes) has grown to intolerable proportions on my game. It used to originally be that only 2 merchants in my game were being affected by this glitch, but now it seems as though the glitch has literally spread like the plague, and ONLY SINCE AFTER my downloading of Honest Hearts and it's corresponding patch, AS WELL AS ONLY AFTER HAVING RETURNED from the Sierra Madre Area of Dead Money.

WHAT USED TO BE ONLY A LET DOWN EFFECTING ONLY 2 MERCHANTS, HAS NOW BECOME A ROADBLOCK FOR MY IN-GAME MONETARY EARNING.

BY MY CURRENT COUNT THE BUG HAS SOMEHOW SPREAD TO EFFECTING ABOUT (12) MERCHANTS IN MY GAME INCLUDING:

-Alexander at The 188 Trading Post, The Generic 188 Trading Post Arms Merchant, Contereras at Camp McCarran, Blake at The Crimson Caravan, Gloria Van Graff at The Silver Rush, BOTH Mick and Ralph, The Gun Runners Vendertron, Torres in The Hidden Valley Bunker, The Hoover Dam Quartermaster Bardon, The Boomer Munitions Manager, and lastly Cliff Briscoe In Novac.

So... Where I'm left now is;

1- Intolerable waitng times for some of those merchants I listed, ESPECIALLY Cliff Briscoe since he has been the MAIN merchant to who I've been selling all my junk to for caps and as such, he now LITERALLY possesses EVERYTHING I've ever collected to sell for caps within his inventory.

2- ALL major sellers of USEFULL and VITAL items such as powerful late game weapons and armor EXCEPT THE GUN RUNNERS VENDERTRON are now all out of such items and now only possess more trivial items such as generic leather armor and miscellaneous junk, all of which are of little to no use to me.

AND POSSIBLY MOST IMPORTANTLY...

3- I no longer have any large Cap quantity carrying Merchants AT ALL. ...This is because even though SOME Merchants might not currently have their items effected by this bug in my game, ALL MERCHANTS in my game right now though, ARE being effected by this bug as it applies to their Cap Count being replenished every 3-4 days like normal.

So you see my issue now.
(...And NO, waiting in front of merchants or saving and reloading in front of merchants is NOT working for me either.)

MY POINT IN THE END IS:
Hopefully this post is a MORE ATTENTION-GRABBING yet STILL POLITE.... KICK-IN-THE-BUTT to Bethesda, than any other possible past complaints about this bug/glitch for them to GET ON THIS and fix it... since I've noticed that as of the latest patch and it's corresponding list of things listed as being corrected by it that you STILL HAVEN'T GOTTEN ON IT and found a fix for it.
Here's also hoping that the proper attention is also going to be payed to the laundry-list of STILL REMAINING bugs/glitches which are being discussed on this forum.

Thanks for your time reading this (I assume)...

Oh, and P.S.
-A reply with an aknowledgement of there being people who actually ARE on this and all the remaining GLARING bugs/glitches would be EXTREMELY courteous and appreciated.

Thanks again.

I can't get Torres to refresh her inventory no matter how long I wait. I hope I don't have more problems as the game goes on.

Correction: Obsidian.

I have a similar thing where the merchant doesn't get any new stock.
I buy everything come back say a in-game week later and they still have a empty inventory, but shop owner like, Gun Runners are restocking and the Dino Bite guy.
Its just the Merchants that walk around the Wastes that don't re-stock for me

The Sink shop has stopped renewing its inventory, the woman in the BoS bunker hasn't restocked since I first traded with her, the quartermaster in hoover dam doesn't restock anymore, van graffs are dead...and the guy in the crimson caravan place doesn't restock either. Only the vendortron restocks so thats my only source of ammo/mods/weapons etc. I'm hoping for a patch when either LR comes out or GRA.

I'm having the same problem. Every vendor I go to has the same things from the time before, and they dont' restock their caps.