does it only happen with specific content (HD vs SD, local channels vs non-locals) or with anything you record ?
does it happen when you're watching live TV or when you're playing back something you recorded previously ?
This is a configurable behaviour.
Hit menu then 8 (Preferences) then 2 (favorites).
Selecting "Guide Button" will switch lists when pressing guide repeatedly, selecting "Guide Popup" will bring up a list with the favorites when you hit guide.
I also have a Maxtor OneTouch 4 and was having the power boot issue with my 612. It is in fact possible to configure the Maxtor to never spin down, I verified it fixed the issue of the STB not seeing the external HDD.
You need to use the Maxtor manager software that came with the HDD by running...
what audio output are you using ?
also, what do you mean by "the feed to delay and stop when going through the guide" ? A/V in the video window ? just audio ? just video ?