IMHO it's quite reasonable to remove the Mindless-granted immunity when a creature gains an Int score, but RAW those seem to be separate things, and a normal Ooze thus gains immunity from two separate sources:
- Source one: http://www.d20srd.org/srd/specialAbi...m#nonabilities
- Source two: http://www.d20srd.org/srd/typesSubtypes.htm#oozeType

Furthermore, due to poor editing, the Ooze traits say:

Quote Originally Posted by SRD
Mindless: No Intelligence score, and immunity to all mind-affecting effects (charms, compulsions, phantasms, patterns, and morale effects).
Since the immunity clause isn't dependent on the no-Intelligence clause, removing the former would not negate the latter.

It should have read like this:

Quote Originally Posted by Better SRD
Mindless: Because oozes have no Intelligence score, they gain immunity to all mind-affecting effects (including charms, compulsions, phantasms, patterns, and morale effects).

It should be the case that the ooze traits are merely repeating / summarizing the nonability text, and that the mind-affecting immunity has a single source (intelligence nonability).