I am using Crazydomain.com.au hosting service and after they upgraded web hosting, our website is down.

We haven't touched any code and used to work properly (www.laptoppanel.com.au), but they said our web coding has problem.
Here is the error message each time open the website.
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Warning: require_once(/home/laptoppa/public_html/system/startup.php) [function.require-once]: failed to open stream: No such file or directory in /home1/laptoppa/public_html/index.php on line 21
Fatal error: require_once() [function.require]: Failed opening required '/home/laptoppa/public_html/system/startup.php' (include_path='.:/usr/lib/php') in /home1/laptoppa/public_html/index.php on line 21
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Is anyone can give me some idea?
Cheers,
Michael