You most certainly can have traction issues from over inflation -- 'specially if they're over inflated as much as you say... From Honda-Tech:
"An over-inflated tire can bounce on surface roughnesses. This can cause dangerous interruptions in traction, particularly if it happens during cornering."
"...decreased traction on marginal surfaces, unpredictable responces during suspension upsets, excessive rebound as the tire bounces over bumps as opposed to absorbing the shock, and yes - given enough time, predictable wear (tire compound sensitive)..."
Some feel over-inflating saves on gas due to reduced traction patch, and lower friction... That's fine in a four-wheeled vehicle... different story on our little ponies...
As Detrich said: 33 and 36, front and back, respectively, unless you're carrying a passenger or a howitzer...