I get the following error when I compile my apex classes:

line -1, column -1: Method 'CodeCoverage' exceeds the maximum number of allowed op codes. Please break this method into multiple, smaller methods.
line -1, column -1: Previous load of class failed: CodeCoverageTest: line -1, column -1: Method 'CodeCoverage' exceeds the maximum number of allowed op codes. Please break this method into multiple, smaller methods.

repeats...

repeats...

repeats...

I had never received this error before in my sandbox. I have not changed anything in the apex since I last ran the compliation.

Any suggestions as to what has caused this?