Fatal Error under Win 2003 Server

My host moved my very well working WP (1.5) from a windows 2000 server to a 2003 server. SInce the move I have the following errors:

Warning: main(./wp-blog-header.php): failed to open stream: No such file or directory in c:\XX\xxxx\xxx\xxx\index.php on line 4

Fatal error: main(): Failed opening required ‘./wp-blog-header.php’ (include_path=’.;c:\php4\pear’) in c:\XX\xxxx\xxx\xxx\index.php on line 4

My index is in the same directory as all other files (root).

I have searched the forum and attempted the solutions that were provided, mostly for b2. I have installed the new wp-blog-header.php (1.5.1), I have deleted, re-uploaded, and reinstalled WP. I have edited the $abspath to directly reflect the path.

I can get into the admin panel and everything works well, though it is real slow. My Gallery and forum work fine. All info in the database, which I also deleted for a fresh install, is correct as far as paths and such go.

Any suggestions?

Thanks