POI limit from POI Loader


I have a Garmin Legend HCx with a 2 GB microSD card.
I have succesfully copied several .csv files to my Garmin using POI Loader.
I have copied one thousand postcodes, for example, but if I try 10,000 the operation fails.
I believed that the limit on the number of POIs able to be copied in this manner was only dictated by the size of the microSD card, which, in this case should not be an issue.
Does POI LOader impose its own limit within one .csv file, or might there be another reason the operation fails?
I thank you in anticipation.