USB keeps disconnecting and reconnecting on microcontroller
If your "own board" is not a PCB then all bets are off (if you prototyped this by hand). If it is a PCB then you need to find out where the problem is occurring in the system. Proablems like this could come from many things, so you need to verify that each piece of the system is working.

1) If you think its the clock, then run a timer test and see if it matches up with a reference clock.

2) It could be software. Remove your code and make a loop back test to and from your host, you could also see if the data lines of the USB are noisy.

3) You could also get some usb sniffing software that you run on the host and see if its your processor that is causing the usb to drop out or the hardware. Here is a reference on USB data flow.