Importing Products

Can anyone help?

I am trying to import an Excel spreadsheet which according to instructions I can import upto 1500 items at a time but but I have over 3000. I reduced the file to 1400 and then 1000 and then 900 because I keep getting the same error massage that you can't import more than 1500 items at a time.

Any ideas why I am getting this error message.

Thanks

Andrew