Contributing to a SEP IRA and later filing as unemployed

[Parlay Slow]

In 2006 I filed as unemployed because the amount of write offs I could have made filing as a professional poker player did not compensate for having to pay FICA tax.

This year I am aiming to file as a professional -- mostly because I would like to max out the $42k contribution to a SEP IRA. I am planning to contribute throughout the year, 5-10k at a time. What if at the end of the year, I decide I no longer want to file as a professional? Will I be looking at costly penalties to liquidate the SEP?