If your table has over 255 fields in it, it is very likely that it may not be Normalized, which could cause other problems in using the data (depending on the level of complexity of your database).
I would recommend trying to normalize the data a little more before importing it (which will probably have to be worked out with whoever is providing the data).
There should be some links out there on how to Normalize your data. If you need help finding those links, please post back.