cracking a domain cachedump

[slawson]

When I processed the file using hash type 1000 I used the --username parameter and Oclhashcat recognized the hashes that were in the file, but it didn't crack it. I ran the same scan using hash type 1100 and oclhashcat cracked one of the hashes.

Can you clear me up on why the hash type 1000 would scan but not crack?