@OP: When PS2ESDL doesn't seem to be doing anything, unplug and re-connect your USB device. If that causes further activity, do that whenever the console seems to be waiting for something (E.g. nothing seems to be loading but the game has not loaded up yet).
There are some USB enclosures like that, and it basically means that your enclosure might not be compatible with the way PS2ESDL and OPL handles it.
(All my enclosures were like that, but they did work with PS2ESDL at least)
Unmodified SCPH-77006 with SM 3.6
SCPH-39006 with M-chip modchip, SCPH-10281 NA and refurb Seagate 80GB HDD
SCPH-10000 v1.00 with SCPH-10190 PCMCIA NA and SCPH-20400 HDD unit