I had this exact problem and managed to diagnose it.

The problem is the Delay pot. When I opened up the memory boy I noticed that there was vertical movement with the shaft. When the shaft was elevated the memory boy kicked in and worked, But soon as it dropped down it cut out. I tried to remedy this with some wire around the shaft to stop it slipping but this was a very, very temporary fix.
Eventually after half an hour the shaft completely came away and the pedal was essentially dead. The only remedy was to unmount the broken pot and replace it with another one, simple right?!
Unfortunately after spending many days searching for a replacement pot which is a very easy fix, I finally came to the conclusion that these must be custom made pots making it impossible to fix without one. (c100k pot)
I contacted electro harmonix to ask for a supplier or if I could buy one off of the company which i was then told it had to be an internal manufacturer fix.
Since finding this out I have now sold every electro harmonix pedal i own and have advised every guitarist and bassist I know to stay well clear of these products, being a guitar tech thats a whole lot of guitarists.
I dont think im the only person who feels that pedals should be completely self serviceable? and knowing that once a pot goes (very common) this essentially means, buy a new one or pay as much as the pedal is worth to fix it.
And this is all because of a part which costs less than £1 retail?!
Very Poor!