Custom columns changed after update

Hi,

I have some custom columns that I use to pull the year, month, week number, and day of year from an existing date column.  The past two updates have changed these so that I am no longer able to edit the step.  When I created the column I was able to access the step at any time, change the name, edit the formula, etc.  The first update after that caused a pop up window to appear stating that an error occured and a preview could not be generated.  This only occured on columns where I was pulling the date informaiton.  The update that just occured changed it so that I can open that step, but now I get an "invoke custom function" and it appears blank, but my date information is still being generated correctly.  Do i need to put my formula back in so that it continues to work properly? 

Thanks,

Jim