Many thanks. I had suspected that my customisation of the STANDARD ERROR template may have caused a problem over the weekend. So I reverted that template back to the original in my test install (and found another way of achieving the result I was aiming for so I can revert to the original in live also). I should have mentioned that I have been using my test install (/testvb/) since, with the standard template, to work on the PP integration.
With Chuck's pointer, I was able to eliminate the 3 errors that were appearing on my error log, relating to the following files not being found:
vbulletin_md5.
js
vbulletin_global.
js
vbulletin_menu.
js
These were caused by relative references in the following VB3 standard templates: "STANDARD_ERROR" and "headinclude". I've amended these 2 templates and am not getting the errors in the log now...
Unfortunately, I mistook the errors in the log as being related to the main problem I'm having, since the behaviour reported above is still occuring and I'm getting the following when I attempt to log in to PP directly (which is what was being displayed before also, although I didn't mention it):
"Internal Server Error, this is an error with your script, check your error log for more information."
What's more, there's nothing being posted in the error log that I'm looking at. Since I'm not very technical, I'm wondering if there's more than one error log and I'm looking at the wrong one, or perhaps it's common for this generic error to not have an error message posted?
In any case, I'm not sure where to go from here?