Embattled multi-level marketing firm Mannatech (NASDAQ: MTEX) has fired its independent auditor, Grant Thornton, after the auditor gave the company an ultimatum: Remove Chairman and founder Sam Caster from the company or find yourself another auditor.

And so Mannatech put out a press release announcing that the company had engaged BDO Seidman as its new independent auditor. Why would Grant Thornton have a problem with Mr. Caster? Well in July, the Texas Attorney General sued the company for making false and misleading claims about its products. Then in August, Caster resigned from his role as CEO to, according to the press release, "focus his efforts on working with field sales leaders to transition to Mannatech's new global wellness sales program.""

Right. Basically, he resigned to devote more time to Mannatech. He's also come under fire for using his role in the company to tout his religious beliefs, and many observers feel that Mannatech has cultivated a cult-like atmosphere among its distributors.

Amazingly, the stock didn't react negatively to the dismissal of the auditor following the ultimatum. If the auditor demands that the Chairman be fired, shouldn't investors be concerned too?