I have written a VFP6.0 application which consists of a modal main form with buttons which call other forms. It works fine on several PCs running all flavours of Windows. On one PC, however, the main form appears but pressing any button just flashes the next form on screen and returns to the main (just like trying to run a non-modal main form). This PC is the boss's - he who installs all sorts of strange software to show he's "the expert". Presumably one of these has put in a version of some DLL which stops the VFP application from working properly. Can anyone suggest how I can find out what's happening, please?