DNS Issues

Hey guys,
I switched my site to another dedicated machine that I own about 2 weeks ago. I did all the setup stuff like I normally do through WHM to get the server setup and ready and finally did the nameserver IP switch on the domain.

The problem is, some people are still seeing the old server off and on, and it has been 2 weeks... It is not a huge percentage, but after reviewing some statistics, probably 5% (which is quite a bit) of my website traffic is still going through the old server. Some users have reported to me that it is off and on between the old server and new.

Is there something I set up wrong possibly? This issue did occur for me personally for about a week when I did the switch (seems much longer than switches I have done in the past), but seems to have cleared up since.

Any help is appreciated. Thanks.