You said "when it was new." How old is it now? I have a LaCie CD burner that failed within the one-year period and LaCie fixed it and sent it back without problem. That was a good 18 months ago and -- knock on wood -- have had no problems since.
You are doing everything correctly in terms of dismounting and powering down the unit, correct?
I mostlyh wanted to say that I, too, trust the LaCie brand and would buy again from them without problem. It is possible, of course, that you have a lemon. Have you asked for a new drive, instead of just repairs? And what have they said is wrong with it?