Expected one Contribution but found 25
Since Imran is on CiviCRM Spark, I had a quick look at the issue. I think it was caused by the field mapping, where the import was trying to import the "Contribution Status", but there wasn't a status for "paid out", causing the import to fail.

So I changed the import mapping to ignore the import status (since the file only completed contributions), and it seems to have resolved the issue.

ADD-ON: this also happens when you try import Contributions with status=completed (as opposed to Completed)!