How were you taught how to spell "dilemma"?

Everywhere today the spelling is "dilemma", yet many people still use "dilemna" claiming that's the way they were taught it in school.

There is even a website dedicated to this specific instance of the Mass Memory Discrepancy Effect - it's at dilemna.info.

Could this be a side effect of the pronunciation?

There is also evidence this discrepancy could be related to the age or the country the speaker is from. In the UK nearly everyone just knows it as "Dilemma" and doesn't even know there is an alternative, yet those claiming otherwise seem to be from the US. 

Spell checkers

The word "dilemma" originates from the Greek word "lemma", so the argument for no "n" is stonger bearing that in mind.

Is the impression that the "n" is present but silent playing a part in this?

Schooling

People even report being taught to use the "n" at school, and actually being marked as incorrect when they didn't in spelling tests. 

This is another one where people are reporting "flip-flops", in that it was one way when they first looked, but coming back to it found it was the other.