Upgrade to 1.18 failed on webhosted Installation
You are right. More information is necessary.
My wiki is installed on a hosted server. I do not have shell access. So I downloaded the update and copied everything via ftp to the web. In the moment it is running. It seems, that some the extension "Configure" caused the problem why I had no further access, I switched it off and so I could finish the installation.
The problem I do have now is that texvc has a new configuration and formulas are not displayed (parser error). With MW1.17. there was a workaround to have it running on a hosted server. But now .... I will post a new support request.
Thank you for your trouble...
Best Regards HJG
Note, math has moved out of core to extension:Math. You will need to install that extension for math stuff to continue working.