Sony's latest range of Memory Sticks won't work with some of its Vaio computers, Sony has warned.

The news is the second admission in a week from the company that a new version of one of its products isn't completely backwards compatible. Late last week, Sony said a new version of the PlayStation 2 due in November had problems running almost 50 existing software titles.

The card problem concerns three new Memory Sticks - the 1GB Pro Duo, 2GB Pro card and 2GB Pro Duo card. The 2GB cards went on sale in September and the 1GB card will go on sale this week. None of them however will 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 comes in the Vaio type V, M and P range. (The exact models are: VGC-V202RB, V202, V201, V172B, V172EB, V172S, V171B, V171, VGC-M50B/S, M30B/W, M30/W and M70/W, and PCV-P101.)

The compatibility problems stem from changes in the internal components used inside of the cards, said a Sony spokesman. Sony launched Memory Stick Pro in January 2003. At the time the company said the format specified versions of the card up to 32GB and a 2GB card was being developed.