I've gotten the letter from the Jarl of Falkreath to visit him about becoming Thane and purchasing land, but neither the Jarl or his Steward will even speak to me. Not a single dialog option is available. They both just stand in the war-room and won't come out no matter how long I wait.

I've completed all Rare Gift quest (Except for Siddgeirs Black-Briar Mead quest because he won't initiate dialog) and CANNOT start the "Kill the Bandit Leader" quest because, once again, he won't talk to me to get the quest started. I have no mods installed. I have no side missions in my queue.

I started a brand new playthrough after running into this problem with my 1st level 30 character....I reinstalled the game (On Steam) and started a brand new character hoping that would fix this bug, didn't help at all.

Did you do the Dark Brotherhood questline? If you've done so, and killed Helvard, your disposition with Siddgeir is too low. Also, once you got the letter, his "Rare Gift" quest won't ever be available.

http://en.uesp.net/wiki/Skyrim:Thane_of_Falkreath has some console entries which may help to fix the disposition problem. Also, there's a mod which allows buying the properties from the stewards without quests: http://www.nexusmods.com/skyrim/mods/66511/?- that might help you out.

I haven't started the Dark Brotherhood quest...in fact, Helvard is standing right beside the Jarl and his Steward alive and well in the war-room. Won't let me talk to him either.

I've tried numerous console commands including but not limited to setting his disposition to very friendly (although I checked his friendly rank and he was a friend before I set it higher). They all complete the quest and remove it from my quest log...but that doesn't solve the problem of me not being able to talk to either the Jarl or Steward so I can't become Thane or accept quest from the Jarl or Steward.

I've researched the problem on Google and came across 100's of others experiencing the same problem on other forums (reddit, GameFAQ etc....).

Well, try the mod then. I've never had an issue (though I never bother with the HF houses any more - there's so many BETTER ones out there..... http://www.nexusmods.com/skyrim/mods/75903/? for instance) and my game's modded to hellangone (seriously - 200 mods and counting)....

I appreciate it but I think I'll just wait for the Special Edition to come out in October and hope Bethesda will have fixed it for that version. I agree there are better mods out there, but I paid good money for the HearthFire DLC and so to not be able to even start it is pretty frustrating.

AFAIK, Beth isn't fixing bugs in the SE. Bug fixes are done by the community. If you aren't using http://www.nexusmods.com/skyrim/mods/71214/?, you should be.

I tried USLEEP and the Unofficial Hearthstone Fix from the Nexus...Neither worked. If Bethesda is going to leave the bug fixing up to the modders, I guess myself and a whole bunch of others on Reddit and a zillion other forums posting about this bug are just outta luck.

USLEEP needs to be installed period. If you're not using it, then your game is going to have issues. What's with the unwillingness to use mods?

I said I tried USLEEP and the Unofficial Hearthfire Patch....neither worked.

Well.... sorry then. USLEEP is important. You need to have it installed. Period. If you're not willing to go there.... I can't help you. Basically though - USLEEP is all you need, you don't need to use any of the other "unofficial patches". They're rolled into USLEEP now. Make sure you have the latest version.

I said I had USLEEP installed. Period. Version 3.0.4a. It's not just me. A google search of "Jarl Falkreath Bug" or "Can't speak to Jarl Falkreath" turns up 1,000's of forum post.

Yah, most of them from years back. Someone else may be able to help you more with this.