How do I limit multiple hits from same IP that happen within a second.

I am constantly getting 4 or more hits from the same IP at the exact same second.  The only time I see this happen it is always the same browser and os version:Mozilla/4.0 (compatible; MSIE 5.00; Windows 98)

Example:

525608      2005.04.10 17:55:43      xxx.xxx.xxx.xxx      xxx.xxx.xxx.xxx      Mozilla/4.0 (compatible; MSIE 5.00; Windows 98)            
525607      2005.04.10 17:55:43      xxx.xxx.xxx.xxx      xxx.xxx.xxx.xxx      Mozilla/4.0 (compatible; MSIE 5.00; Windows 98)            
525606      2005.04.10 17:55:42      xxx.xxx.xxx.xxx      xxx.xxx.xxx.xxx      Mozilla/4.0 (compatible; MSIE 5.00; Windows 98)            
525605      2005.04.10 17:55:42      xxx.xxx.xxx.xxx      xxx.xxx.xxx.xxx      Mozilla/4.0 (compatible; MSIE 5.00; Windows 98)            
525604      2005.04.10 17:55:42      xxx.xxx.xxx.xxx      xxx.xxx.xxx.xxx      Mozilla/4.0 (compatible; MSIE 5.00; Windows 98)

The IP address will vary, and they never resolve to a domain name.  Sometimes it will show the referrer, which is almost always the same.  It is (I assume) Chinese based, I cannot read it.

Anyone have any suggestions?  I keep going thru the list, and blocking the IP address, but they keep coming from other IPs as well.