Unable to load debug symbols


i try to debug a LPC1768 controller. The build process finished correct, but the following debugging aborts with an error like:

Unable to load debug symbols: c:\ProgramData\Mbed Studio\mbed-studio-tools\gcc\bin\arm-none-eabi-objdump.exe: ‘\Programmierung\c\Mbed Programs\mbed-os-example-blinky2\BUILD\LPC1768\ARMC6\mbed-os-example-blinky2.elf’: No such file

In the path of build directory is missing drive letter “e” and the colon “:”.
I hope somebody can help me.
Thanks in advance…