Primer-y user error

"So did adjusting the magnesium concentration fix your PCR?"
"Well, actually it looks like there's not much difference between the different concentrations."
"So what was your problem?"
"Er...I had the primers at the wrong concentration so I adjusted them for this second PCR and it looks okay now."
"You think it was a problem with the primer concentration?"
"Er...yeah."

Forgetting to add primers results in a primer concentration of 0 μM, which is definitely a problem, so technically I wasn't lying to cover embarrassment =D