I was getting that same error.
As long as you're sure you partitioned the card right (fat32 as first and ext3 as second) , fat32 is primary/active, try creating the /data/sdext2 (it did not exist on my unit, and if it doesn't on yours, that might be a good sign), and copy all 3 files that kennyminot posted. You might want also want to recheck the permissions for the files are:
for the external/internal modified vold files
I used the MiniTool Partition Wizard to partition my card.