Build Error Object reference not set to an instance of an object

Hi

I have an application which when complied with vb.net 2003 will give one
Build Error showing the in task list. The build window reports no errors and
rebuild was all sucessful. The error is Object reference not set to an
instance of an object.
at line 0, if I click on the error it will take me to line 1 of the code
for a form, the command at this line is Imports
System.Text.RegularExpressions.

Otherwise the application is fine, it compiles and operates correctly, i can
create a new project using the same lines of code for this form and I do not
get this error.

Can anyone give me any pointers to what may be causing this behaviour

Thanks