addition to previous post: there you can read that:

"AddDefaultCharset directive
Syntax: AddDefaultCharset On|Off|charset
Context: all
Status: core
Default: AddDefaultCharset Off
Compatibility: AddDefaultCharset is only available in Apache 1.3.12 and later
This directive specifies the name of the character set that will be added to any response that does not have any parameter on the content type in the HTTP headers. This will override any character set specified in the body of the document via a META tag. A setting of AddDefaultCharset Off disables this functionality. AddDefaultCharset On enables Apache's internal default charset of iso-8859-1 as required by the directive. You can also specify an alternate charset to be used.

For example:

AddDefaultCharset utf-8
Note: This will not have any effect on the Content-Type and character set for default Apache-generated status pages (such as '404 Not Found' or '301 Moved Permanently') because those have an actual character set (that in which the hard-coded page content is written) and don't need to have a default applied."

so you can simply put the AddDefaultCharset On to httpd.conf file and it won't crash the server. it will work the same, but it will fix this problem. i have found another user who has got same problem as me - http://forums.bizhat.com/ftopic2175.html

(if you afraid of this setting, could you simply change it for a while and test some random subdomains.)