I'll tr and make a blog post later on about this. But a quick fix for now:

The function is created, but it's not necessary it's actually used. The quick and dirty way to solve this is to query the database direct, Simply run the query "Select * from tblPage where fkPageTypeID = MY_FUNCTION_TYPE_ID". The function type id can be found by finding the corresponding EPiServer CMS page type in the admin mode. Once you find all pages of the correct page type, simply delete them from EPiServer CMs edit mode.

This might make some pages to behave strange if they use any of the functions you delete, but you can always make a quick check by observering the page name of the functions. The name is "cf_XXX_YYY_ZZZ_WWW" where XXX is the page id of the page that created this function.

Hope this helps for now.

/f

Actually you just need to delete the page that is being referenced by EPiServer. Yo can find out by going to Admin mode - Page Type and look for the funtion from a lsit which starts with [ExtensionSys] YourFunction. Click on there, try to delete the function and EPiServer will tell you what page is being referenced. It comes in a form of a strange ID, so just click on the link that Episerver displays and delete the page. Make sure you also delete it from the recycle bin. Now you can delete the Function