Hi Singer,

You are right! I have solved the problem! The problem arouses when your form contains non-English characters. What I did to solve the problem is to change the option in Control Panel-->Regional and Language options-->Advanced-->"Language for non-Unicode programs" to suit the language I use in the form. It solves the problem immediately!

Thanks very much for everyone of you!

big thank for this solution :D it was my nightmare error

I had the same problem when I converted to Windows XP. It was solved by creating an empty Microsoft Access application and importing the objects from the unhappy one.