DNS problem

[mrmagoo]

I'm running ISPConfig 2.2.15
When I upload a file via ftp I get a lot of ...waiting for the server... also the mysql answers gets slow.
I believe is a dns configuration problem since I have a single IP address for the server and I tested the network, router, etc and everithing works fine, the router internal test reports no significative traffic issues.
I need help to find the problem. Maybe changing the IP address will do the trick
Please tell me what I need to change in the ISPConfig Config files and the server config files (running ubuntu server 6.10 configured with the http://www.howtoforge.com/perfect_setup_ubuntu_6.10)

What is create dns and create dns-mx
Thanks

[edge]

Your FTP problem could be a Ident lookups and reverse dns lookups.

In the proftpd.conf file set IdentLookups and UseReverseDNS to off.

Make sure that you restart proFTPD