...
Now, with that said, it IS possible for the AWL to be polluted and cause problems. Generally this is the result of past misconfiguration or scoring problems that have since been fixed, but the AWL retains the old average and causes score problems, pushing things onto the wrong side of the spam/ham threshold line.
Solution
If you have this problem, you can use spamassassin --remove-addr-from-whitelist to remove any prior knowledge about a given address from the AWL database. If you consult the main spamassassin manpage, there are other commands to force an AWL entry towards the black or white, but use these somewhat cautiously.
...