Insufficient Key Size
Are you running on all 8 cores? This small key is factorable on a PC with an efficient implementation.
The test key doesn't fit the 60-bit modulus given for it. The modulus contained in the given key "MA8CCAlALgKC9d0lAgMBAAE=" is 0x9402e0282f5dd25.
The key that fits the given modulus 0xdf5e743f13f6a1f is "MA8CCA3150PxP2ofAgMBAAE=".
@sqrt2: Good catch! I'm not sure how I made that mistake; I must have generated two different keys and got them mixed up. I'll update the problem with the correct public key now.