503 error usually referrers to the web server traffic being too high for the server. This can happen with a shared IP hosting plan, or it could be that the forum software is holding sessions (when someone logs into the site) open longer than it should. You could try adjusting the session timeout in the vB admin control panel or if your budget can allow it, bump your hosting plan up to the next level. It's a good thing and means the site is getting bigger!
I'm a sys admin at work and I have my own web hosting setup with multiple websites, forums and blogs, so if you have any questions feel free to PM me.
PS - Don't count on the hosting company to respond to any errors. You'll need to contact them first - it's just kinda the way things work.
Error 503 - Service Temporarily Unavailable
This error means that the web server is currently unable to handle your request due to a temporary overload.
Please try to reload the webpage in a few seconds.
If you are the webmaster of this website and you see this error often please contact your web hosting company support for more information.
Internal Server Error
The server encountered an internal error or misconfiguration and was unable to complete your request.
Please contact the server administrator, [email protected] and inform them of the time the error occurred, and anything you might have done that may have caused the error.
More information about this error may be available in the server error log.
Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request
Error 503 - Service Temporarily Unavailable
This error means that the web server is currently unable to handle your request due to a temporary overload.
Please try to reload the webpage in a few seconds.
If you are the webmaster of this website and you see this error often please contact your web hosting company support for more information.