What are you using to partition the card? Did you use Ubuntu to format the ext? Also, are you partitioning with the card in the phone or are you removing it (better)? The thing about the android kernel is it doesn't reload the partition tables (I don't even know if it can without rebooting, but rebooting can hose your partitions if the kernel flushes filesystems to their old locations.) I ended with a really messed up sdcard when I first started because I assumed the android kernel behaved like Ubuntu's.
You may want to
I cannot stress how little faith I now have in modifying partitions through USB access mode.
- remove the sdcard, and insert directly into your Ubuntu box
- backup the fat partition (you need the OpenRecovery files),
- use gparted
- delete all partitions on the sdcard using gparted
- Create a fat32 primary partition leaving 512mb-1gb(1024mb) free for an ext2 (or ext3) partition (I use 1gb ext3)
- Set the boot flag on the fat32 partition.
- create a primary ext2 (or 3) partition in the remaining 512-1gb
- copy back the files from the old fat32 to the new fat32
Il try it where is the patch i' sure my partitions are good.