PDF text extraction error

Using version 6.5.2 - When uploading a PDF the text extraction (sys_textExtraction) raises an error:

"The text extraction failed with result code ‘128’ for file type ‘Adobe Acrobat (PDF)’. The message was: – No output –

Setting the PDFConversion parameter to MULTI raises a corrupt file error.

The PDFs used to upload ok but these errors seem to have started to occur when generated with Adobe Professional 9 - The first line in the PDF file is PDF-1.5.

Anybody else seen this?