Hey, I guess it may be interesting for somebody...
My H320 didn't work well with newer bootloaders (all the custom ones above version 5), so I decided to upgrade it to CompactFlash, so I bought a card (32GB Kingston elite pro x133 from Newegg) and the adapter.
Now, I tried the bootloader from this page:
http://www.rockbox.org/twiki/bin/view/Main/CFModGuide (r16446M-080228)
Also I tried bootloaders from this thread:
http://forums.rockbox.org/index.php?topic=17202.0 (080904)
from this web-page:
http://hendrik.feuerware.com/rockbox.htm (r17607M-080525 and r16184M-080130)
and, also, another one, given me by user pondlife (thanks) - ( r18818M - from oct'08)
Now, the results:
All of them sometimes work

They start correctly maybe 2 times of 3.
1/3 of a time bootloader stuck after showing the version and the voltage,
or sometimes shows error:
I04:IllInstr
003F2AA0
And only pressing reset button helps.
Now, the one from CFMod page (r16446M-080228) works the most reliably. Much better than any other one mentioned here. But if I connect the power cord to it when its off, (and this was the main reason I wanted the upgrade since v5 boots the iRiver stock firmware in this case) it also stucks somewhere in the bootloader.
But the good thing is, if it's loaded it works perfectly.