imho the problem is an unpatched hdloader, in my pro hdl work just fine (but i don't use it). download one of the patcher (like hdl aio, hdlpatch ect) and patch it for no disk seek and don't patch it for stop disc spinning, be sure to use an uncompressed untouched elf.
then try again, you can also try deleting from dms format the new partitions if you think was hdldump but i don't think so
ps2os betatester, ps2tools codev, hdldump frontend dev
6 sony mc w/ps2os 0.2.4, hdl, ps2rmp1.50,ps2mp3...
na+hd maxtor diamondmax 7200 120GB
PS2 SCPH-30004R V6 ÐM$3 V2 firm 2.4 B.4
PS2 SCPH-50003 V9 ÐM$4 PRO firm toxic os 0.1