i don't think I've had problems with this feature before, so we need to dig a bit more before I know what the problem is.
Could you try importing this file:
http://jexpress.bioinfo.no/DiauxicShift.txt ? I have already tested this file by importing it using the Load Tabular Data from the J-Express File tab and had not problems.
I just want to check whether there could be a problem with your file.
AK