Thanks for your reply.
I am using integrated security and access is fine - I tested using a blank QV report with just a connection and basic table in it and it ran. I've commented out all the script on the report I am having issues with (although there are several) and I am gradually adding the scripts back in chunk by chunk so I can hopefully identify the bit it doesn't like, I will post the script that is flagging up the error shortly.
I think I've figured out what it was.
The problem was a connection string in my script which I had set to force 32 bit:
//OLEDB CONNECT32 TO [Provider=SQLOL.......
As the server is a 64 bit operating system I changed the connections to read:
OLEDB CONNECT TO [Provider=SQLOL........"
and it works! Seems that's the answer.
Much appreciated for replying and taking a look though - it prompted me to comment everything out and look line by line.