MSL=Master Subsidy Locak. This article may shed some light on the problem - especiaslly the last paragraph:
CDMA phones can have two six-digit codes; a one-time service programming code (SPC), and the master subsidy lock (MSL). The SPC is can be used to activate a brand new phone onto wireless service, and it works only one time. Not all wireless carriers use the SPC code.
The SPC makes it possible for a consumer to purchase the phone anywhere, call up the provider's toll-free number, and then activate the wireless phone from the directions given by the representative on the other end of the line. After the initial programming, the SPC is no longer valid. This method enables the initial field programming of the phone by the consumer, and now the wireless provider has the knowledge of the only working programming code for your phone for subsequent programming, which is the master subsidy lock.
Once the SPC has been used, the only working programming code for the phone is the MSL. This fact is important to note, because if the phone needs to be reprogrammed for any reason, the MSL must be used. These reasons may include a phone number change, a PRL update, or a firmware upgrade.
For example, if you need to change your phone number because you moved, or perhaps, you purchased the phone second-hand, the phone must be reprogrammed, and to do so requires knowledge of the MSL.
The MSL code is generated by an algorithm based upon the phone's ESN and the specific carrier who originally sold the phone. Each carrier uses a different algorithm to create the MSL code. For example, one carrier would not be able to generate valid MSL codes for a different carrier's cellular phone simply by plugging in the phone's ESN into their algorithm.
NOTE: Be careful when purchasing a second-hand phone, especially from places like eBay. Some wireless carriers, including Sprint PCS, nTelos, and Qwest/US West will NOT activate a phone if it is associated with an account with an outstanding balance. If this is the case, they will not release the MSL, and thus, you will have purchased a paperweight. If you intend to purhcase a second-hand phone for use on one of these carriers, ask the seller for the ESN of the phone and check with the carrier to see if the ESN is clear before completing the transaction.
CorkyG - Tucson, AZ
In my view you cannot claim to have seen something until you have photographed it.... Emile Zola