@Juanito, since the previous poster hadn't responded and the topic is still valid/exists, I was curious if we could research the cause for mcookie.
Environment (last week's attempt):
x86, x64 and Pure64 kernel and image - no boot codes save for tce=UUID
Extensions: Xorg (I tried 7.5 and 7.4 if memory serves, I'd have to check), Xprogs, flwm, wbar *No ATERM during my tests
I used PXE on a mid/hefty dual-core w/ 12G and re-tested in VM to replicate the problem.
All three cores "as is" booted perfectly fine. (I hadn't realized Xvesa hadn't been ported initially, thus when I switched over to Xorg for testing x64)
On x86 and x64 I used tce-load to pull in the extensions -- smooth as glass after I swapped out my Raedon card with something supported in-house without firmware extensions added. (Prior X simply failed to load as expected for an AIW card.) Upon rebooting, everything launched as expected... test complete.
Now... I extracted the extensions and embedded them into the boot image and launched the three new images in their place.
On boot, the first thing (after hardware and network settle) is I launch the files found in tce.installed so that support/dirs/files are created for each.
x86: Flawless.
x64: Failed with mcookie error.
Pure: Wasn't tested as I expected the same as x64.
My guesses would be there's a specific order needing to be launched (extensions) (ie: Xorg-libs before Xorg or similar) OR the tc-config for 64 and/or pure does something prior to launching StartX which isn't in the x86 config (I have not looked into either direction yet as I had to park the attempt for more pressing matters.)
Forgive the thread hijack... it wasn't intentional as I was going to post new until I came across this one still dangling from a few months back and figured if we can sort out the problem, it may also help the initial poster.
Thanks for any feedback anyone can figure out in this matter!
~TJ~