Import of leads failed

Hello,

I am experiencing some difficulty with leads import; the issue is identical if I try to import "my leads" or "my organization leads", with or without lead assignment rules in place.

When I go through the leads import process, I am not able to map certain fields after uploading my xls document: contact first and last name, campaign source. If I proceed and choose to accept ignoring certain columns, the upload animation bar will just stay forever, and nothing is imported at all.

I did some investigation : the mapping and leads upload worked perfectly with another Zoho CRM account (same .xls file). The account for which it is not working is different in the sense that I added lots of customized fields and changed the page layout.

Hopefully this helps understanding my problem.