Thank you for your post.
Unfortunately, I am unable to duplicate the problem. I am using Microsoft Excel 2008. I created a several records/rows with text information including 00123456, 0000424, etc. I save the file and import it into FileMaker Pro 10 text fields, and the data displays in the text fields with leading zeroes. Is there something I can try here to replicate the problem?
I have encountered a similar problem and here is what I have found:
1. To maintain leading zeroes, the source field in Excel must be in text format (see note below).
2. Save file to be imported as an ".xls" file, NOT ".xlsx"!! Filemaker 10 allows you to import from ".xslx" files. I was unable to successfully import fields with leading zeros from an xslx file. Once I tried saving the exact same file as an ".xls" file, import worked perfectly retaining the leading zeros.
Notes: If you continue to encounter problems with your excel data, try formatting an empty column as "Text". Copy the column with your data into the newly created text column and re-import your data. I import accounting data through Excel, so this was an additional step that was required to make the import work properly.
I hope this is helpful to someone who was as baffled as I was for a few moments.