Re: USBTinyISP Problems.. Works 1 out of 20 times...
I have a similar problem. My USBtinyISP used to work perfectly. now I've started to get nothing but mismatch verification errors. I've tried both the power jumper on the usbtinyisp and separate power supplies, etc to no avail. reading and writing fuse bits seems to work fine, but writing to flash doesn't pass verification. It's not the chips themselves (I ruined a perfectly good arduino uno trying to burn a new bootloader via the isp headers, and brand new chips don't work either). I also used to get partial programs to work, but not anymore. I can detect the correct atmega328p device signature, so it's hooked up properly, etc.
It just won't work beyond that.
UPDATE: I was able to repair my arduino uno boards using a leonardo as isp. I think I have a dead usbtinyisp.