For a while in the game I have been encountering an annoying glitch where my character is becoming invisible or seems to be obscured by objects that should be in his background.
Later a second glitch started that was even more annoying - other characters consider him to be empty space. In combat, attacking melee enemies will often step right on the same spot where I am standing, before attacking. This has been annoying particularly when an enemy has ran up to stand on my hex and others shoot at him to hit me instead.

Now I encountered a third bug when trying to use the elevator inside the vault of Vault City. This is the first elevator I encountered in the game. My character becomes invisible when I walk into it. 'Using' the elevator with the hand icon does nothing. Completely stuck. Any suggestions?

re-instal, change your refresh rate, upgrade RAM, graphics card, processor, don't play for so long, don't have other programs running in your background, lower level of detail, etc. etc...