I'm getting a great signal from the router, and I have no problem connecting to it and getting on the internet, however after about 5 or 10 minutes ill lose the internet (while still connected to the network) I can easily disconnect and reconnect, and suddenly I'm online again.
It seems like I get kicked off the internet much faster if I'm downloading or loading many pages at once in different tabs.
Could be you need to adjust the MTU in the router -- default is 1500 and you might start by adjusting in increments of 100 and then fine tune to by 10. A free download of a program like TCPOptimizer may help calibrate your connection.
I think I would also check the firmware version of your router then visit the D-Link site and see if there's a newer version.
I raise this because my neighbours were running a 615 and I accidentally broke into their WPA secured system while testing another wireless router. I wont tell you how, but I was able to reproduce how I'd done it and have heard since that there can be security issues with some D-Link models.
You can sometimes work out if someone else has accessed your system by checking the log (first correct the date the log is using) the router also has a facility to detect who is online.
It's not inconceivable that if someone else is borrowing your service they'll kick you off when you are using a lot of bandwidth.