I recently purchased the Elder Signs: Omens game, and I enjoy playing it quite a bit, even though the first few times were rough because I didn't understand a lot of the mechanics. After a few days though, I finally got the hang of it, and am regularly scoring around the 4500 mark when I win (which is not much, but it's something). 

However, one thing still really bothers me. I'm wondering why is it that I can't use some items with certain people prior to conjuring. For example, right now I have Vincent in  Yuggoth, and even though I have two red glyph items with me, they're "blacked out" and I'm not able to use them. There's no red glyph locks that I can see.

Is there some kind of rule that says only certain people can use certain items, and only at certain locations? 

Thanks for any guidance!

 The red glyph lock is in effect on that picture..
Look to the left, you see all the green circles, and a yellow and a red.. those represent your glyphs, and a green and the red one has a padlock on them, meaning they are locked..

On the map screen, look for a red circle. That circle marks what adventure (or monster at that location) locks the glyph. The circle goes in and out of visibility, so lots of ppl miss that.

It took me a few plays to pick up on that also.  Definately makes it easier to come up with a winning strategy when you are able to use all your items.