To add to the pile, I've also come across this bug. I can use my phone and quick hack, but weapons/grenades and arm weaponry are all disabled. I was quickhacking like a mad man out in the Badlands on a Regina mission when weapons went bye bye, tried reloading, logging all the way out of the game, verifying files through GOG launcher, loading an old save where a cutscene was involved--and to this end, weapons were finally restored but even loading several old saves, weapons were initially disabled throughout; after taking Panam's profoffered sniper did the bug sort itself out temporarily. That said, getting them working again in an old save did not transfer forward.
Fast traveling fixes it until you move your character. Unequipping all items and clothing has no effect.
I'll try the joytoy method later today, but man, I'm way too deep in this character to go backwards.
Amongst the odd behavior, I noticed that the character's arms seem to be telling the game they are not recognized as I couldn't climb ladders, hurdle obstacles or windows, or vault up to a higher area. I could mount personal motorcycles and requested cars, but hijacking was not working. Several elements also began to fail like hud icons, enemy chevrons, etc. I was hoping taking down a cyberpsycho would fix it, and managed to down one with quickhacks only, but it did not recover anything I didn't already have for functionality.
Fast traveling fixes it until you move your character. Unequipping all items and clothing has no effect.
I'll try the joytoy method later today, but man, I'm way too deep in this character to go backwards.
Amongst the odd behavior, I noticed that the character's arms seem to be telling the game they are not recognized as I couldn't climb ladders, hurdle obstacles or windows, or vault up to a higher area. I could mount personal motorcycles and requested cars, but hijacking was not working. Several elements also began to fail like hud icons, enemy chevrons, etc. I was hoping taking down a cyberpsycho would fix it, and managed to down one with quickhacks only, but it did not recover anything I didn't already have for functionality.
You are a life saver my dude! This does indeed do the trick. After being able to getting full functionality back and a long session with Panam, I finally went and did the Play if Safe and felt a wave of "now that's more like it!" from this game. Stunning mission top to bottom.
I had this issue for the first time yesterday and I got really desperate because I didn't have any other saved game but the automatic ones.
Well, I found a workaround for this and it works to everyone, I believe. Look in the map for a secondary mission where there's a shooting competition. As soon as you get there and the competition starts, your guns will be automatically drawn.
Okay guys, I have had the same issue when searching for a solution, what I did was wanting to add mods to my legendary trenchcoat, however action blocked, I removed the special clothing set and it allowed me to get on with my day....try something like that with your own weapons and/or clothing? 
Now have action blocked pop-up with most (90%) weapons and though it doesn't say anything most (95%) clothing will not equip, makes equip sound, but that's all. Have stripped character of all items, sold old items, dismantled old items, tried purchasing new items, tried crafting items, same issue. Tried the Joy Toy fix, didn't work. Can use items that are already equipped, but can't exchange anything. Also tried fresh install of game, zero luck. Level 50 character, 600+ hours. Really would rather not have to start over from scratch.
You use mods ?
You don't have a save before the problem occurred ?
Tried with and without mods, seems to infect all saves even back to the start. goes away on building a new character though.
You could try (if you have a good net connection), to copy/past your saves in another folder (for not loosing them) and reinstall completly the game (no files remaining). With luck, it's not really in the saves, but somewhere in game files.
But I think, it'll remains in the saves, unfortunately
Already tried that. Definitely in the saves. Using C++ now to read the save files to try and find if the issue area can be removed without breaking the save.You could try (if you have a good net connection), to copy/past your saves in another folder (for not loosing them) and reinstall completly the game (no files remaining). With luck, it's not really in the saves, but somewhere in game files.
But I think, it'll remains in the saves, unfortunately