According to Intuit, Error Code C=343 can occur when:
- you’re not running the latest release of QuickBooks
- 1 of 2 Microsoft Core XML Services .dll files is unregistered, missing, or damaged
Confirm you’re running the latest release of QuickBooks. To verify your QuickBooks release, from within QuickBooks press F2 to display the Product Information window. The Product shows both your version and release in the upper left corner.
If the problem persists, either MSXML3.DLL or MSXML4.DLL is unregistered, missing, or damaged. The first troubleshooting step is to re-register both of these files while QuickBooks is not running and then re-start QuickBooks to see if the problem has been resolved. If the error recurs, you’ll need to download and re-install Microsoft’s Core XML services.
See our related article on another error involving Microsoft’s XML Parser, an unrecoverable error has occurred exception msxml could not cocreate instance.
For more information on the troubleshooting steps to resolve Error Code C=343, consult this Intuit knowledge base article.