FORTUNE — Dear Annie: When I accepted my current job about a year ago, I felt lucky to get it. I had been out of work (following a layoff) for about five months and this seemed like a great opportunity to move my career forward. Unfortunately, it hasn’t worked out that way. The culture at this company is bureaucratic and stifling, and my colleagues have all been here forever and treat me like an “outsider.” As a result, I’m not getting challenging assignments, and instead I’m getting stuck with the tedious tasks no one else wants. When it’s time to make a decision, my boss seems to solicit everyone’s opinion except mine.

I really hate coming to work in the morning. I’ve never been a clock-watcher, but this place is turning me into one: I can’t wait to get out of here at the end of the day, and spend every Sunday dreading Monday. Still, it is a “good” job with a steady paycheck, and I know millions of people would trade places with me in a heartbeat. What do you and your readers think? Should I start looking for another job, or just try to grin and bear it? — Treading Water

Dear T.W.: Yikes. If it’s true that misery loves company, you may be heartened by a few statistics from the U.S. Department of Labor: The “quits rate” — the percentage of people who voluntarily leave their jobs every month — plummeted in early 2010 to a low of 1%, or half its pre-recession level. It has since crept up a bit, to 1.5% in July and 1.6% in September (the latest available) of 2011.

Clearly, the sluggish economy and slowdown in hiring are keeping plenty of people stuck in jobs they don’t like. But, intriguingly, it seems that many of those who do choose to walk are doing it within a short time: Almost half (46%) of employees who quit do so within 18 months of being hired, says a new study by recruiting and applicant-tracking software developer Bullhorn.

The most common culprit, according to the report: A bad cultural fit — that is, an employee’s sense that he or she just doesn’t belong, and consequently can’t get ahead. Sound familiar?

Kate Wendleton, president of national career-counseling network The Five O’Clock Club, has identified eight specific symptoms of a bad fit. “If you’ve noticed three or more of these warning signs,” she says, “it’s time to update your resume and launch a job search.”

1. Your values don’t match those of your coworkers or higher-ups. Wendleton has seen many instances of employees who don’t fit in because they won’t go along with unethical (or even illegal) practices, but a clash in values can take many other forms. Your description of your company as “bureaucratic and stifling” suggests the culture isn’t right for you.

2. Your boss doesn’t like you. This probably applies if “you don’t support his approach or agenda, or she never solicits your opinion,” says Wendleton, adding, “If you’ve ever done or said anything to undermine your boss, you might as well get out now.”

3. Your peers don’t like you. Being treated like an “outsider” is a clue. “If you feel isolated, gossiped about, and excluded from the inner workings of the organization, and if you have no sense of camaraderie at work,” Wendleton says, “it’s time to start planning to move on.”

4. You don’t get assignments that make the best use of your abilities. When the fit is bad, all the plum projects go to others, while you get the ones that play to your weaknesses, Wendleton says — a sign that “your boss doesn’t trust your judgment or believe you will do a good job.”

5. You always get stuck with the “grunt work” no one else wants. “You can lobby for better projects and ask for assignments that will showcase your skills and heighten your credibility,” Wendleton notes — but don’t be surprised if you don’t get them.

6. You are excluded from meetings that your peers are invited to. Obviously, this is unmistakable evidence of outsider status, says Wendleton: “You don’t feel that your ideas are valued or your contributions are central to the company.”

7. Everyone else at your level has an office, while you have a cubicle in the hallway. Whatever your formal title, Wendleton observes, a lousy workspace “telegraphs your place in the informal hierarchy loudly and clearly.”

8. You dread going to work. “If the idea of going to work makes you anxious or physically sick, and if you find yourself counting the hours until you can leave, you need to start job hunting,” says Wendleton. Life’s too short for this.

Your question suggests you’re beset by at least six of these eight problems, twice the “three or more” that should have you aiming for the exit. It’s far easier to find a job when you already have one, so why not think of your current position as a stepping stone to your next one?

And don’t put it off: It’s best not to wait until you’re so demoralized that you can’t be “up” for your job hunt. Good luck.

Talkback: Have you recently said “I quit!” despite the dismal job market? Have you ever felt stuck in the wrong job? What did you do about it? Leave a comment below.