Three models of Memory Stick Pro memory card recently launched by Sony and one to be launched tomorrow won't work with some of the company's Vaio desktop computers, the company said yesterday.

The announcement is the second admission within a week from the company that a new version of one of its products isn't completely backwards compatible. Late last week, Sony Computer Entertainment, the division responsible for the Playstation game console, said that a new version of the Playstation 2 due on sale in Japan on 23 November had problems running almost 50 existing software titles.

The card problem concerns the MSX-M1GST, 1GB Memory Stick Pro Duo card; the MSX-2GS, a 2GB Memory Stick Pro card; the MSX-M2GS, a 2GB Memory Stick Pro Duo card; and the PSP-MP1G, a 1GB Memory Stick Pro Duo card, Sony said in a statement. The latter card is scheduled to go on sale in Japan on Friday branded for use with the PSP (Playstation Portable) while the two 2GB cards went on sale on 9 September.

The cards won't work with the internal Memory Stick readers in several models of Vaio computer and users should either use an external reader or lower capacity cards, the company said. The affected computers are the Vaio type V, models VGC-V202RB, V202, V201, V172B, V172EB, V172S, V171B and V171; Vaio type M, models VGC-M50B/S, M30B/W, M30/W and M70/W; and Vaio P, model PCV-P101. The problem also affects some models sold in Europe.

The compatibility problems stem from changes in the internal components used inside of the cards, said Daichi Yamafuji, a Sony spokesman in Tokyo.

Sony launched Memory Stick Pro at the CES (Consumer Electronics Show) in Las Vegas, US, in January 2003. The computers that have problems reading the cards were on sale in Japan at various times between late 2003 and late 2004.