Symptoms:
In SDL TMS 2011 SP5 CU1 and earlier, pre-translated SDLXLIFF bilingual files are overwritten during the Pre-Processing stage, regardless of their match score.

Explanation:
When Pre-Processing pre-translated XLIFF-based bilingual files, the pre-translated match is overwritten during the ApplyTM stage. The initial match is replaced with the best match from the translation memory, even if the translation memory score is lower.

Resolution:
At the point of applying the translation memory match to the bilingual file, it is considered that the bilingual file may already contain a match (or a pre-translation). The translation memory match is only applied if the score is greater than that of the existing match.