I removed the hard disk from my EeePC and used it with Debian Squeeze on a 16GB SD card. It wasn't fast, but it was all solid-state, and that's important to me.
However, lately it had started misbehaving. When recovering from sleep it'd lose all fonts (everything was displayed in squares), files could not be found and programs would stop working, and in a short time the system would become completely useless.

Then after a while it started doing it regardless of sleep mode; I'd turn it on, do something, and it would work for a while - or maybe not - and then screw up. As an example, I noticed that unmounting partitions from gparted would do it almost always, but unmounting them from shell wouldn't. Sometimes simply opening the browser would cause this weird crash. When shutting the system off it'd complain about the ext4 partition, though I don't remember exactly what it said.

I thought it was Debian that had somehow screwed itself up (or I had...), so I wiped the card and installed Ubuntu Netbook on it. I was quite surprised to see that that, too, failed in the exact same way.

I'd blame the SD card, but the strange thing is, the data on it is perfectly fine. In fact, I temporarily fixed the problem by reinstalling the hard drive, dd-ing the whole SD card on it and then expanding the partition over the unused space. From this setup, the system works perfectly - using the same data from which it used to fail when running from the SD card.

Anyone can shed some light on what exactly happened here?

Thanks.

Did you mount the partitions with the "noatime" option to prevent writing to the device after a read?

A pendrive and SD card will have extremely slow writes. If you powered down or disconnected the card before the cache was emptied, and the card was ready, you could cause corruption as well.

Running Linux off a 16GB pendrive or SD Card, is a case where you don't want to have a swap partition.

Mounted using noatime. No swap partition.

It worked well for a good while, so I don't think slow write speeds have anything to do with this.