Hi Stuart Hemming,
Thank you for getting back to us.
Can you please let us know if the upload process has been interrupted due to some reason. For example you have selected upload, however while uploading you have canceled the upload. Then uploaded again. Or if there has been an error the first time.
We have had similar problems when the upload did not complete for some reason however those issues were addressed in Sitefinity 4.1.
Also please note that if the upload process is canceled the uploaded cannot clean up the temporary folder which holds the temp files until they are added to the library. In this case you will have to manually clean them from ~/App_Data/Sitefinity/Temp
the Telerik team
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