64 bit prod web server pre-compile problems??

I've got an asp.net website that runs fine from VS.NET on my client.

If I deploy the site by moving it to the Test web server it works
fine.

If I precompile the site on the Test server that goes well as well.

If I deploy the sources to my prod server which is 64 bit I get this
error:

An attempt was made to load a program with an incorrect format.
(Exception from HRESULT: 0x8007000B)
Description: An unhandled exception occurred during the execution of
the current web request. Please review the stack trace for more
information about the error and where it originated in the code.

Exception Details: System.BadImageFormatException: An attempt was made
to load a program with an incorrect format. (Exception from HRESULT:
0x8007000B)


If I attempt to pre-compile, using aspnet_compiler -v /
myvirtualpathfromwebroot

I get this error:

web.config(70): error ASPCONFIG: Theme 'RTTheme' cannot be found in
the application or global theme directories.

I check and RTTheme is there under app_Themes

This is what the web.config entry looks like, and themes work fine on
DEV and TEST :

<pages styleSheetTheme="RTTheme">