What the Heck??? Quicktime Movie Problem....

Question

Hi. I really hope someone can help.
I basically want to create a Quicktime Movie; however, when completed, the item properties are not always the same as the custom Quicktime Movie settings I chose.
Here are my sequence settings in FCP:
HD (960x720) (16:9)
Pixel Aspect Ratio: HD (960x720)
Anamorphic box unchecked
Editing Timebase: 23.98
Quicktime Video Settings: DVCPRO HD 720p60.
That's the timeline I work on - no problems.
Then I try to export using Quicktime Movie with these Custom settings:
Frame Size: 960x720 - HD (960x720) (16:9)
Pixel Aspect Ratio: HD (960x720)
Anamorphic box unchecked
Editing Timebase: 23.98
Timecode Rate: Same As Editing Timebase
Quicktime Video Settings: DVCPRO HD 720p60.
*SOMETIMES IT WORKS, SOMETIMES IT DOESN'T!*
When it does work, nothing changes; the Item Properties are the same as the settings I chose upon export and the Quicktime Movie does not need to be rendered when imported back to the original sequence.
However, at times the settings change as such:
Frame Size: 1280x720
Pixel Aspect: Square.
NOTE: I have never been able to successfully export the entire sequence (TRT:00:02:56). When it did work and the settings remained the same, I only attempted to export a small portion of the sequence.
The sequence is comprised of only audio/video, a couple of slugs, and a couple of title cards.
Thanks

Answer 1

Thanks for the reply.
Current settings did not make a difference since I essentially was using current settings by manually plugging them in under "Custom."
Unfortunately, I had to plug-and-chug my way through. After two hours and over 30 QuickTime movies, I found three trouble spots:
1) A slug at the beginning;
2) A cross dissolve between two clips;
3) A cut within one clip.
VERY ODD!!! Once I removed these conditions, e.g., eliminated the slug and started hard on the clip, removed the cross dissolve, and eliminating the cut, I was able to successfully create a QuickTime movie of the entire sequence at the current settings.
Why? So weird!!! The thing that confuses me the most is that the three conditions were so different (seemingly, at least). I couldn't find any common situation.
Any thoughts anyone???