Apache shutsdown error

[cluelesshost808]

Don't know why but apache cannot find my user file
This is the message in the error log:

[Thu May 16 14:16:28.279389 2013] [auth_basic:error] [pid 716:tid 1668] [client xxxx.xxx.xx.x:xxxxxx] AH01618: user root not found: /xampp/

thanks for your help