Portage 2.0.7 on my system (a p3-900 with ATA100 harddrive) has been taking 10+ minutes to generate the initial dep cache after an upgrade from 2.0.5. (after 10 minutes, its _still_ going). Masking 2.0.6 and 2.0.7 (based on ChangeLog info)
You're going to have the *exact* same issue with 2.0.5. We currently wipe out /var/cache/edb/dep every time portage is upgraded. I'm going to guess that if you downgrade to 2.0.5, you'll still have the same issue? You *can't* (!!!) just go ahead and mask versions of Portage without talking to me first, unless it's an absolute and total emergency, which this isn't. 2.0.5 has a bunch of big bugs so you've just made things worse for users. I'm unmasking 2.0.7.