Thanks Deepak,
The file permissions are correct. We have tracked the problem down to another cause.
It turns out that most releases of MaxDB do not support hostnames on HP-UX 11 longer than 8 characters. (This is despite SAP Notes like 611361 which state that SAP supports hostnames of up to 13 characters).
Our hostnames standard here are 10 characters in length. The MaxDB SDBINST script checks the hostname and truncates it to 8 characters, causing the error.
The problem is documented here:
http://maxdb.sap.com/webpts?wptsdetail=yes&ErrorType=0&ErrorID=1242198
Cheers, Phil G.