As I said before:

Whenever a new file is downloaded, the hashing process takes significantly longer. Whenever LW loads, it rehahses everything, which takes almost no time; however, to hash a new file takes much longer.

yes, but before 3.6.x it didn't take this long. ~10min/mb

I don't know then.

I don't believe any changes have been made to how hashing is done since that version.

However, perhaps preferences, such as whether or not you are an ultrapeer or RAM allocation were changed during installation.