Not just amateurs, Tony. I was in the revival of Kismet in the West End in the late 1970s, and there's a sequence towards the end where a trio of dances is introduced by the character of Omar Khayyam, announced as it were, from a scroll. The wonderful old character actor playing the part had real difficulties with the three speeches, which were very badly phrased, and at some point during the previews I rewrote them for him, just a couple of nips and tucks and rebalancing of sentences, which he found much easier and the director either never noticed, or was happy with, since the changes stayed. I'd actually pasted the revision into the scroll, so he never actually got round to learning the revision properly, reading the speeches straight from the prop every night.

One night, however, as the scene got underway, I was nudged by another member of the company who had originally suggested the re-write:
"This should be interesting", he hissed.
" - What?" I answered.
" - The scroll," he replied.
" - But he hasn't got it."
" - Exactly."

  The poor man had left his scroll in the dressing room; no time to go back and get it. What he had in his memory was a vague recollection of what he'd originally learnt, plus a patchy idea of the revision he'd been using for several weeks. His stumbling and fumbling over the mixture was simultaneously hysterical and agonising, not helped by smirks and titters from onstage and the Pit: it's strange how everybody suddenly knows someone else's part so well that they can identify the slightest deviation from it, let alone the massive detours and false trails that we were treated to that night.

By the following evening the actor had learnt the new version off by heart: he never so much as glanced at the scroll again, even though thereafter it was always with him.....

My favourite of all time, though, was when someone came on stage disguised as someone else. He boldly announced: "My name is..." and forgot who he was supposed to be.

Stressed Eric or stress test. Who is going to pass a stress test?

*tuts*

They both look like me. I don't want to practise, I don't want to practise, I don't want to prlactise.
There are stupid mistakes sometimes (lapses of concentration, tiredness?).

I am practising because I am worriied.

This will surely help. A dose of good music, googling and humour cures many illnesses.

How absolutely horrible, Mary, sorry to hear that. Makes me think I ought to be more assiduous about backing things up - if my laptop disappeared now I think I'd have to disappear too.