Small problem with MySQL database error

Client is a philatelic auction house. After an auction 2 reports are available 1) a prices realised summary which only shows sold lots and 2) the entire sale on a lot by lot basis which shows price realised after lot description. This is where problem is. An unsold lot should show either no price or 'UNSOLD' but currently is placing the price realised of the previous lot and thus skews the real result.

So if you look for example at lot 986 from this link:
http://grosvenorauctions.com/dyn_pages/historic_sale_summary.php?show_h_sale_no=61&page=20#
you can see a price of £400 but the lot was unsold and the previous lot price has been used.
See also the summary of prices realised here:
http://grosvenorauctions.com/dyn_pages/prices_realised_specificsale.php?Sale_no=61&button=Submit
where lot 986 has no report.

The data is generated from a Filemaker Pro output CSV file and then a php program reads the file and uploads it into mysql. It is possible that that is where the problem occurs - i.e instead of generating a 'NULL' it is making it up!