There is a known issue of a delay when PXE booted for jobs or Initial or Managed Deployment windows to show up.
We upgraded to 7.5 to take advantage of ability for techs to image via the managed deployment window options so there would be less need to have inexeperienced techs in the CMS console. It works.. but it's painfully slow.
I timed it and from the time you select the preboot config, it takes 1 min and 15 seconds for the dos window to minimize in PXE and then another 2 mins for the managed deployment window to come up with imaging options. It doesn't sound like a lot, until you're the tech sitting there for over 3 minutes waiting for it to finally appear. Even knowing it was coming, I've inadvertantly been distracted and then missed the window (which I have set to show for 80 seconds).
I understand this is a known issue - but it would be great if this delay could be somehow cut in half (or better)!