Dear Rick,
sometimes the error 43 occurs only in a specific web application, I don't understand the cause because the server has a lot of RAM and not even an attachment larger than 16 Mb is loaded.
However error 43, unlike all other errors which are handled by error procedure, blocks the application by generating a window.
Any suggestions on how to handle this error?
Many thanks for support

That looks like FoxPro running out of heap space.

Check in Task Manager and see if the application is using a ton of memory which might indicate there's a reference leak of something not getting release. Not uncommon with Web Control Framework pages - make sure you unload any dynamically loaded components explicitly.