Probation in general has been discussed here previously, although I'm not sure whether it was here, on the Peds board or on the General board. I'd suggest a search.
Because I've encountered a program on probation as well, and was curious how often this occurs, I did a search on the ACGME site. This is how things break down for Peds in the US, by state.
A without anything else means all programs in a state were accredited, either Continue Full Accreditation or Full Accreditation.
I have noted only programs on probation or with provisional accreditation.
State # of programs
ALABAMA: 2 programs, all accredited
ALASKA: 0 prog.
ARIZONA: 3, accredited
ARKANSAS: 1, A
CALIFORNIA: 20, A
COLORADO: 1, A
CONNECTICUT: 2, A + 1 withdrawn
DELAWARE: 1, A
DC: 3, 1 A + 2 on probation (Howard and Georgetown)
FLORIDA: 7, A
GEORGIA: 5, 4 A + 1 on provisional acc. (Morehouse)
HAWAII: 2, A
IDAHO: 0
ILLINOIS: 11, 10 acc. + 1 on probation (Cook County)
INDIANA: 2, A
IOWA: 2, A
KANSAS: 2, A
KENTUCKY: 2, A
LOUISIANA: 3, A
MAINE: 1, A
MARYLAND: 4, A
MASS.:5, A
MICHIGAN: 9, 8 A +1 withdrawn
MINNESOTA: 2, A
MISSISSIPPI:2, A
MISSOURI: 4, A
MONTANA: 0
NEBRASKA: 1, A
NEVADA: 1, A
NEW HAMPSHIRE: 1, A
NEW JERSEY: 9, A
NEW MEXICO: 1, A
NEW YORK: 33, 28A + 2 withdrawn + 2 provisional (LICH, St Barnabas) + 1 probation (New York Medical College/Metropolitan)
N. CAROLINA: 5, A
N.DAKOTA: 0
OHIO: 9, A
OKLAHOMA: 2, A
OREGON: 1, A
PENN:8, A
PUERTO RICO: 5, 3 A + 2 on probation ( Universidad Central del Caribe and San Juan Bautista Med Ctr)
RHODE ISALND: 1, A
S. CAROLINA: 2, A
S. DAKOTA: 0
TENN: 4, A
TEXAS: 12, A
UTAH: 1, A
VERMONT: 1, A
VIRGINIA: 5, A
WASHINGTON: 2, A
WEST VIRGINIA: 3, A
WISCONSIN: 3, 2a + probation (U of Wisonsin @ Madison)
WYOMING: 0
So there really aren't that many programs on probation overall. I'd really look for good answers before considering a program on probation--it's a clear risk.