What Problem? A year ago, Martin Weiss and his small insurance rating service were sued by Health Net, the big Woodland Hills-based health plan. The suit, accusing Florida-based Weiss Research of libel, slander and other wrongdoing, came after Weiss published a financial review of 13 big HMOs that gave Health Net a D rating and said it was deep in debt and financially shaky. A pretrial conference is scheduled Friday in federal court in Los Angeles. Weiss says his legal bills already exceed $350,000 but that he vows to fight “to the bitter end.” Health Net says Weiss’ analysis was flawed, that the company’s financial health is “terrific” and notes that Health Net scored a C in his latest report.