>I have the following code. It had worked forever with no problems.
>Today I failed. The ShellExecute function is now returning 2.

Today You failed? I think I can not help you there <g>

If ShellExecute returns a value > 32 it was successfull, otherwise it will return one of this errors, in your case apparently is File not found
(copied from the docs)

0 The operating system is out of memory or resources.
ERROR_FILE_NOT_FOUND The specified file was not found.
ERROR_PATH_NOT_FOUND The specified path was not found.
ERROR_BAD_FORMAT The .exe file is invalid (non-Microsoft Win32® .exe or error in .exe image).
SE_ERR_ACCESSDENIED The operating system denied access to the specified file.
SE_ERR_ASSOCINCOMPLETE The file name association is incomplete or invalid.
SE_ERR_DDEBUSY The Dynamic Data Exchange (DDE) transaction could not be completed because other DDE transactions were being processed.
SE_ERR_DDEFAIL The DDE transaction failed.
SE_ERR_DDETIMEOUT The DDE transaction could not be completed because the request timed out.
SE_ERR_DLLNOTFOUND The specified dynamic-link library (DLL) was not found.
SE_ERR_FNF The specified file was not found.
SE_ERR_NOASSOC There is no application associated with the given file name extension. This error will also be returned if you attempt to print a file that is not printable.
SE_ERR_OOM There was not enough memory to complete the operation.
SE_ERR_PNF The specified path was not found.
SE_ERR_SHARE A sharing violation occurred

And the values for SE errors are (I think those ERROR_ have the same value as the corresponding SE_ constants):

#define SE_ERR_FNF      2
#define SE_ERR_PNF      3
#define SE_ERR_ACCESSDENIED     5
#define SE_ERR_OOM      8
#define SE_ERR_DLLNOTFOUND      32
#define SE_ERR_SHARE    26
#define SE_ERR_ASSOCINCOMPLETE  27
#define SE_ERR_DDETIMEOUT       28
#define SE_ERR_DDEFAIL  29
#define SE_ERR_DDEBUSY  30
#define SE_ERR_NOASSOC  31