Correct the error. It's much, much more likely to be yours (of from whoever made that particular spreadsheet) than Microsofts. If you really can't find it, try on another PC to see if it's a problem with your copy of Excel. Then reinstall.
It's not clear from your post what "stops working" exactly means. That alone makes it quite difficult to have other ideas, such as "Did you disable automatic recalculation by accident? Then enable it again." That's one of the lesser known features of Excel, not a bug or an error. It's at most a user error to press the wrong keys.
Windows 7 - I have a excel spreadsheet that acts as a check register
and keeps track of balances and expenses by G/L code ( gas, water electric, deposits, etc. Works fine all year but stops working after 147 entries. Any ideas

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