Mental blonk 

A state of confusion brought about by the excessive intake of alcohol.

"I've got a mental blonk, I can't remember where I put my keys".

Mental blonk by Jakerator June 19, 2009

mental blank 

The occurrence of temporarily forgetting something that's in the back of your mind, somewhere. An embarrassing situation encountered when required to remember somebody’s name or when you’re a quiz show contestant.

Oh man! I thought a phrase to look up on UD earlier, but now that I'm on the site I can’t remember what the hell it was. Damn mental blank!

mental blank by Šteggs October 7, 2007