Lightroom 5.7.1 error message when exporting

Hi all,

When exporting a photo from Lightroom 5.7.1 I am now receiving an error message that reads as follows:

Unable to Export:

An internal error has occurred.  Win 32 API error 2 ("The system cannot find the file specified.") when calling ShellExecuteEXW from AgWorkspace.shellExecute.

I tried to repair the installation and also uninstalled and reinstalled from the FTP site.  

It appears it does export to where I want, but occasionally locks up and I cannot close the program.

Windows 10, Intel Core i7 with 16 GB RAM.

Thanks in advance.

Howard

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