compilation error: file exists in both in both 'c:\WINNT\Microsoft.NET\Framework\v2.0.50727

[ABCL]

Hi All
we have asp.net web appliction that runs on the .net 2.0, I have
found that, some times we are getting the compilation error on the
production server
the Mastreapge.master.cs file
exists in both in both 'c:\WINNT\Microsoft.NET\Framework
\v2.0.50727\Temporary ASP.NET Files\app\0605c7ad
\509a24c8\myweb_Web_1234567.dll' and 'c:\WINNT\Microsoft.NET\Framework
\v2.0.50727\Temporary ASP.NET Files\app\0605c7ad
\509a24c8\myweb_Web_oubr7ud1.dll'


if we get this error, we just remove all files under "'c:\WINNT
\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET files" directiry

But i do not have idea,Why is it happening?

does anyone know about it?

Thanks