Mega 2560 per ISP flashen

Hallo,

wenn ich jetzt nach den ganzen Versuche per USB wieder flashen will kommt folgendes:

avrdude: Version 5.11, compiled on Sep  2 2011 at 19:38:36
         Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
         Copyright (c) 2007-2009 Joerg Wunsch

         System wide configuration file is "D:\Programme\Arduino-1.0.1\hardware/tools/avr/etc/avrdude.conf"

         Using Port                    : \\.\COM17
         Using Programmer              : stk500v2
         Overriding Baud Rate          : 115200
avrdude: Send: . [1b] . [01] . [00] . [01] . [0e] . [01] . [14] 
avrdude: Recv: 
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: Send: . [1b] . [01] . [00] . [01] . [0e] . [01] . [14] 
avrdude: Recv: 
avrdude: stk500v2_ReceiveMessage(): timeout
avrdude: Send: . [1b] . [01] . [00] . [01] . [0e] . [01] . [14]