Automation Error After Some Iterations?

Creating a spreadsheet to inventory cups each day. When a macro was invoked do the following:

-unprotect the worksheet

-cut/paste the completed sheet below the current

-bring in the values form the previous day's inventory

-set protection on new spreadsheet to lock the cells

-blank out old values

-reprotect the worksheet

Pretty straightforward and seems to work fine for a few iterations, then crashes with "Run-time error '-2147417848 (80010108)': Automation error. The object invoked has disconnected from its clients.".

As FYI, this code was mostly generated using a record macro session, so no variables involved.

Here is a screenshot of the spreadsheet as it sits now:

spreadsheet.png

Here is the code:
Sub NewDay()
'
' NewDay Macro

' Create new day and copy cup count from previous day[code]....