Hey, when you've already achieved perfection, why keep messing around? ;)

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Okay, in all seriousness: it sounds like a glitch, but... what race/class combinations do you have in your party? Only fighters, paladins, barbarians, rangers and larks can use magic weapons at all, and rangers can only use those up to +2.

Also, have you raised the strength of any of your front line warriors; and if so, by how much? It's been years since I've played, but there may be minimum requirements to wield certain weapons.

Last but not least [MINOR SPOILER] there are weapons you can find (in fact, which you eventually must find) which are more powerful than the ones you can buy; and those weapons should be able to be equipped by anyone in your party.

Judging from the subject title, I think it can be safely assumed that they have already discovered the weapons you're referring to. I'm thinking it's either a stat restriction, level restriction, or possibly a Mark restriction, but I don't recall the latter ever being a thing and it certainly doesn't seem to be documented anywhere.

I believe Exotic weapons are P. What does the game do when you attempt to ready weapon P?

Basicly, when I try and equip anything beyond the 2 handed sword the computer beeps at me. As if I am entering a illegal command.

Exotics should be usable by anyone in the party.