ok, so i guess 5.00 M33-5 was released and then quickly replaced with M33-6 or something. bug fix i guess. anyways...
Changes in 5.00 M33-6:
* A setting has been added to recovery, that, when enabled it may increase memory stick reading speed. (only on the psp, not in the pc). By default it is disabled. If you installed 3.71 fatmsmod, do not use this setting, as its performance with 3.71 driver has not been tested. Instead, reinstall 5.00 m33-4 using dc8 and update to 5.00 m33-6.
* Fixed a bug that made unbootable psp without memory stick or with a bad one.
DOWNLOAD
or use network update.