Error uploading files to a page

Hi,

a week ago my website started displaying an error when files are uploaded to blogs/pages etc. I had upgraded from 5.9 to 5.10 a week previously, but as my users upload files daily using the 'File Attachments', I know that the upgrade was successful. The error users get in Firefox (normal user or site Admin) is contained in a pop up windows box, with the words:

An error occurred: Unspecified error

You can then click the OK button to close the msg box, at the same time the Attach-scroll bar disappears and your left with the standard text and no file listing.

In IE7, the upload status bar just keeps scrolling along forever. With a bit of trial and error, I found out that the upload does actually complete (in FireFox and IE), however the file ends up uploading twice. The second one will end with a '_0', ie: filename_0.pdf If you go back and edit the page, you will find 2 files listed. The first file will have the 'lISTED' BOX UNTICKED, THE SECOND file_0 will be ticked for listing. The user can then succesfully delete the first file.

Apache error log says the following error msg:

PHP Fatal error: Cannot pass parameter 1 by reference in {drupalroot}/modules/upload/upload.module on line 894, referer: http://www.example.com.au/node/add/page

this is the offending line 894 which lies in the 'upload_js' function:

$function('upload_js', $form);

I have tried using the Devel. module to list out various variables ie: dvr($module);. The $form was a large array of data, however when listing out the $module from the previous line, it said it was a Null. Is this correct? If not, what should it be?

I can narrow down the fault to a 3 hour window 7 days or so ago. at 11:35 a file upload was successfully and at 15:25 a file was uploaded twice. This begs the question, what caused this? Whilst I am sure something must have changed, I haven't been able to see anything. The Watchdog log doesn't show anything special.

Having noticed that the upload.module was modified in the 5.9 to 5.10 upgrade, I used the drupal.org cvs website to run a diff on the two versions, and saw that apart from a header line only one line was added. I did try commenting out the line, and as I suspected, it didn't help as I received the same error. I am not using any extra uploading module like 'Asset', but I am using the 'Node images' Ver: 5.x-3.x-dev module. I have tried disabling the module, to no effect - same problem.

This site has been running successfully since Drupal Ver 4.7 and was upgraded to 5.1 in Oct. 2007. Any ideas? Any thoughts on the next step in tracking this down?

Thanks.

Cheers,

Paul