Wal-Mart de Mexico, S.A.B. de C.V. (ADR OTC: WMMVY) has frozen prices on more than 500 basic products that are private label Wal-Mart brands, as well as the cost of tortillas (to MX$5.05 pesos per kilogram), in all Wal-Mart Super Centers in Mexico, according to an Excelsior.com report.  The price freeze will remain in effect until December 31, 2008.