Googled around for a bit and found out that this is a fairly common problem that is spread across multiple platforms.
Apple support states that "Your DNS server(s) or your router may be affected by DNS prefetching in Safari 5.0.1 or later". This is due to Safari 5.0's DNS prefetching mechanism, which appears to send more requests than allowed by some ISPs. This issue may also cause problems with some routers.
Steps to disable DNS-prefetching:
Open the run dialog with WIN+R
Execute the following command (including quotes):
"\Program Files (x86)\Common Files\Apple\Apple Application Support\defaults.exe" write com.apple.safari WebKitDNSPrefetchingEnabled -boolean false
Restart Safari
To re-enable DNS-prefetching:
Open the run dialog with WIN+R
Execute the following command (including quotes):
"\Program Files (x86)\Common Files\Apple\Apple Application Support\defaults.exe" delete com.apple.safari WebKitDNSPrefetchingEnabled
Restart Safari