Last week, this website started to give me a blank screen when ever I attempted to login to it via the WordPress dashboard. It was most concerning as aside from this the site appeared to be running fine.
I did some digging to figure out why and found it to be a common problem from a few sources that WordPress would do this due to a number of reasons. I modified my php.ini file to enable logging of all errors to a file and then restarted the application pool that runs my website.
In the php-errors.log file I found the culprit – the line below showed me the issue.
[18-Sep-2011 23:57:18] PHP Fatal error: Call to undefined function is_multisite() in C:\inetpub\www.sbsfaq.com\wp-content\plugins\backupbuddy\classes\admin.php on line 16
I went into the plugins folder and renamed the plugin folder backupbuddy to something else and then performed an IISRESET. Voila – I could login to my WordPress console once more. Now to dig into why BackupBuddy thought this was an issue.