RCN is blaming its inability late last month to offer CableCARDs to a customer on Motorola. The problem, RCN told the FCC last week, was a shortage in cards following the vendor’s switch over from single-stream CableCARDs (S-Cards) to new multi-directional cards (M-Cards). "Unfortunately, after the S-Card had been discontinued there was a delay in Motorola’s production and delivery of the new M-Cards, causing our existing inventory of S-Cards to be seriously depleted," RCN wrote in a letter to the affected customer. The letter was part of RCN’s public FCC filing because the customer, David Yoffie, had brought the incident to the FCC’s attention, saying it was reason for the Commission not to grant RCN’s request for a waiver to the July 1 set-top integration ban. Motorola did not respond to requests for comment by deadline. RCN said its 1st shipment of M-Cards came Apr 9 and it was able to "ameliorate to some extent the backlog of orders." As of Apr 16, it had received a 2nd shipment and was expecting another later that week. The overbuilder said it has also placed an additional order because of heavier than expected demand for the cards, partially due to the release of the TiVo Series 3 DVR that requires 2 cards for its 2 tuners.