well, try to un-comment that line in the config file by removing the #.
It should default to 0 though, afaik.
If its set to 2 that would explain the long time. The last time I had mine set to 2 it never came back from scanning. So Im fine with 0 and some weird tagged files 😉
NSLU2 formatted is ext3, yes. So thats not an issue. ext3 is blazing fast on the slug.
Some NTFS implementations f.i. arent.