Black files

Hello, I have a weird problem. After grade my files In Resolve 12 and exporting back to final cut pro x I opened the xml file and every thing is in order. Fcp render the optimazation for files but after that beguns another render cycle and the files in the timeline goes to black, same thing when I playback the sequence.
I close it and open fcp and sequence and files are fine, I mean, I can playback sequence and the files shows an image in timeline but in the first editing pause all clips goes to black again. And the endless render begin.
I have tried erasing my preferences in fcp, I relinked all files in fcp, I change the name's files and reimport to fcp but nothing of these helps.
Any ideas? I really apreciate your help, I'm in a midle of feature film grading
Thanks in advanced!
Octavio Gasca