Shimano Ultegra chaninrings on Truvativ Elita Tandem crank
I can't say for sure if the chainrings work on that crank in your particular configuration. It sounds like they should.
Keep in mind that road triples are inherently troublesome (though some might disagree with me) and require a little more mucking with to get adjusted. If your front shifter doesn't have trim/half shifts between full shifts, you may need to let out the cable on your front derailleur a little and actually let the chain drag slightly against the cage when in those extreme gears on the cassette. This will keep the chain off of the shifting pins of the big chain ring. Not real awesome but it might be the best you can get away with on your current setup.
It also sounds like your chainline is not optimal. Are there any spacers between the bottom bracket shell and the outboard bearing cups? If so, you may need to move one to the drive side. If not, don't add them.
Worst case you may need to go back to Truvativ rings. Hard to say for sure as it's always difficult to diagnose bikes over the internet.