The white screen of death (between part 2 and part 3)

After a few hours rest I've come back to my PC to write the next blog entry about producing the Hello World! application. I switch on my PC and server, load up the IP.Board home page and ...

Nothing. Completely blank white screen, no HTML source generated. AdminCP works fine, so what's gone wrong?

I don't remember editing any skin files, but maybe I have. So I edit conf_global.php to switch off IN_DEV mode and force IP.Board to use the default skin rather than the one in the master_skin folder. I reload the IP.Board home page and ...

An error message from PHP about class rss_output_calendar being declared more than once.

A logon to the Linux box and searh for 'rss_output_calendar' tells me that it's in 2 places:

/admin/applications_addon/ips/calendar/extensions/rssOutput.php
/admin/applications_addon/other/helloapp/extensions/rssOutput.php

So a quick edit of /admin/applications_addon/other/helloapp/extensions/rssOutput.php to change

class rss_output_calendar

to

class rss_output_helloapp

and the home page works again.

There must have been some caching going on I guess while I've been resting, because that certainly wasn't happening before. The most irritating thing is that I had to turn IN_DEV mode OFF to get the error message to display. That doesn't seem right somehow.

I switch on IN_DEV mode again, and a few minutes later I get another error:

Fatal error: Cannot redeclare class calendarMemberSync in <path>/admin/applications_addon/other/helloapp/extensions/memberSync.php on line 38

That's another edit I need to do, but why did I get the error this time with IN_DEV mode ON? Blowed if I know.