My conclusion was that Zaurus SD card driver is horrible piece of crap.
Try MMC or even MMCPlus if it can be used with newer Zaurii.
Yes, I've heard that SD I/O relies on an extra software layer for Digital Rights Media stuff that can cause all sorts of problems, and that MMC cards don't have this (this also has the side-effect that MMC cards have slightly more real capacity than SD cards of the same nominal capacity).
There are quite a few 2Gb MMC cards available and I would love to have this kind of capacity on my Z, but I haven't found any sources of these cards near where I live where I could walk in and try one out. If anyone has any experience with these, please post.
The cheapest one I've seen is the ADATA/Samsung one (on various traders on ebay). I've also seen a 3G MMC by
Microdia, but I don't know of any retailers yet.
In principle, MMCPlus should be backwards-compatible with standard MMC and SD devices - you just won't get the increased read/write speed that MMCPlus offers in a MMC slot because the extra connectors on the card aren't used.
Regards,
P.