I disagree with your statement here:
"People who routinely work a lot of overtime typically are either incompetent or in the wrong job. Some OT once in a while is inevitable. Lots of overtime, all the time, is a danger signal"
I have been involved in jobs where overtime is necessary due to workload and working 5 to 10 hours extra a week is normal. The situation that makes this happen is overwork by employer, or unwillingness to add resources due to COST of said additional resources(namely people) I also know of others who have done this for years because they get the JOB DONE and working a bit extra is what it takes to get it done.
Nearly every case where this occurs there is a "ONE MAN SHOW" (or woman). Until the actual cost of health, due to overwork, or overtime reach the cost of a salaried person, I say keep working the overtime so long as you get paid or otherwise acceptably-compensated for the extra time.
I do not believe that being a one person show working overtime a lot is a "DANGER SIGNAL" either.
But that ONE-PERSON must also accept the fact that vacation is not happening either since you wll be "THE PERSON" And yet some IT shops do just that, they have ONE PERSON running the whole shebang and when he/she is out, they wait or attempt to get them to fix something remotely, all the while interrupting their time away from work.
I disagree that it is a two sided issue.
Incompetence or Wrong Job.
Some jobs just are full of work and short on resources, others are full of resource and short on work.
In the IT/IS world, you often switch from FEAST to FAMINE mode rather quickly and back again and most people learn to handle it.
If the original poster is losing 10K in the deal, then a talk with Management and some numbers on paper as well as the suggestion by another reply of doing the "I'm sorry, I can't do that till tomorrow Dave" scenario are great ideas.
Leaving will just put you into another trial period another pot-of-troubles/customers/equipment/networks etc.
At least you arlready KNOW this network.
If getting the compensation back fails to satisfy your needs, SURE, get a better job. It always helps to have a current resume. Even when you are NOT looking.
You should not feel so PUNISHED by the change to salaried from hourly. The amounts of overtime mentioned would be caught by most employers anyway and they would move to end as much of it as possible. Overtime is 1.5 times wages (sometimes more) So it is an accounting issue to reduce salary-expense for them and a good business decision.
The fact that it made you go down in income 10K is a rare occurance in my opinion.
Also remember that YOU WORK for the company.
They do not OWN YOU. Scheduled overtime, extra work is much better on your social life than work that is last minute, (aka, OFFICE SPACE Movie style) "I'm gonna need you to come in this weekend)"
On unscheduled events there needs to be ground rules for compensation on time off or extra pay.
Because that is what is FAIR.
Then again if the company calls you more than twice a month for after-hours emergency work, then it may be time to ADD A RESOURCE and/or Request ON-CALL PAY.
On-Call Pay would be extra pay you receive just for being AVAILABLE, then if the call is resolved in less than two hours you still get paid for two (or whatever minimum is set)
Also remember that as you move up the corporate ladder, Salaries go UP and so do the hours that one winds up working just to get the JOB DONE since responsibility also increases. The trick is to surround yourself with competent & responsible people that you may delegate toward, those tasks for which you have no real time.
Till you get those resources, work the overtime sparingly, and let the company know that they are asking ABOVE AND BEYOND normal working conditions and yet, the compensation is less than fair.