(FORTUNE Magazine) – 'Injustices in the workplace abound--but are they all the result of discrimination?" asks a reader named Elizabeth, who incidentally knows bias when she sees it: Way back in 1969, a bank officer informed her that she'd make a great management trainee if only she weren't female. Still, in a fairly typical response to the Aug. 16 column about what seems to be keeping many women and minorities out of top corporate jobs, she goes on, "Don't overlook simple managerial chaos, or that the chemistry is simply not right in a particular company or--although we may not want to admit it--we have some kind of alienating personality trait. There are no guarantees for anybody. We must take charge of our own careers, obstacles and all, and not rely on the diversity nannies to make things comfortable for us."

A couple of dozen African-American managers, about half of whom are also women, wrote to say that they are doing just that. "I am a CPA who recently earned an MBA, and I have done everything your column suggested, e.g., I took on the tasks no one else wanted, let my immediate boss know I was eager to move up, and so on," says a black woman middle manager who asked to be anonymous. Results? Zip. "To make a long story short, the final advice offered [by author Roland Nolen, who was quoted in the earlier column] not to 'try to fix the unfixable' is on point." She quit her old job and joined a different company.

"In today's go-go economy, leaving an unpromising position is not a bad solution," notes a self-described "African-American male manager who has had to personally navigate some rough waters in FORTUNE 500 companies." However, from what he's seen, women and minorities who are puzzled by their own lack of advancement often suffer from an excess of, well, tact (however misguided) on the part of peers and bosses: "People are afraid to criticize you as bluntly as they would a white guy, for fear of seeming racist or sexist or both." Trouble is, a good kick in the pants can be a career booster: "If you think you're doing fine, when others don't agree but are afraid to say so, you probably won't modify traits or actions that are the real tiebreakers in determining who gets the plum assignments and promotions."

What can you do about it? Ask your supervisor to be candid with you about your faults, and develop a network of people, including peers and subordinates, whom you can trust to give you honest feedback on a regular basis. And stay cool. Writes our correspondent: "There is often value even in dumb or petty criticisms (if only to show you how dumb and petty your co-workers can be)."

Some new research supports his point, by the way. A study by recruiting firm Korn/Ferry International, which examined how the highest-ranking minority executives in U.S. companies got where they are, says that 71% relied on guidance, including well-timed criticism, from "informal mentors." For a detailed and provocative analysis of how African-American stars have risen, get hold of Breaking Through: The Making of Minority Executives in Corporate America, by David A. Thomas and John J. Gabarro (Harvard Business School Press, $29.95).

Many thanks to Mark Miner at Pittsburgh law firm Buchanan Ingersoll (www.bipc.com) for sending the September issue of Pennsylvania Employment Law Letter, with its tips on preventing workplace violence (Sept. 27). Two great Websites for more information: Centers for Disease Control at www.cdc.gov/niosh/violrisk.html; and the Occupational Safety and Health Administration, at www.osha.gov/oshinfo/priorities/violence.html. A reader named Patricia sent some wise words too: Be careful how you fire people. "Making a real effort to minimize the psychological and emotional impact [of a firing] is every bit as important as adhering to the legal technicalities."

And finally, on the ever popular topic of office romance (Sept. 6), I got a truly stunning volume of mail, mostly from people who are proud of the fact that they've managed to keep their personal business a secret from their employers--often right up until the wedding invitations went out or, in one case, well past that. Writes one amazingly discreet manager: "My boss had no idea I was married to [a VP in another division] until the day he saw us in the company parking lot with two of our three children." Marvelous. Everybody's happy--even, for once, the lawyers.