Java + AuthGroupFile = Error

I have a simple Java Applet, and when I use "AuthGroupFile" in .htaccess, I
got the following error in the log:

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401 - Authentication Required for the following files:

HIDDEN-HOST-NAME - - [28/Oct/2005:09:47:39 +0100] "GET /MyApplet.jar
HTTP/1.1" 401 489 "-" "Mozilla/4.0 (Windows XP 5.1) Java/1.5.0_02"

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however, if I use "AuthUserFile" I don't have any errors. Any idea??

HIDDEN-HOST-NAME - - [28/Oct/2005:10:02:19 +0100] "GET /MyApplet.jar
HTTP/1.1" 401 489 "-" "Mozilla/4.0 (Windows XP 5.1) Java/1.5.0_02"
HIDDEN-HOST-NAME - HIDDEN-USERNAME [28/Oct/2005:10:02:19 +0100] "HEAD
/MyApplet.jar HTTP/1.1" 200 0 "-" "-"
HIDDEN-HOST-NAME - HIDDEN-USERNAME [28/Oct/2005:10:02:19 +0100] "GET
/MyApplet.jar HTTP/1.1" 200 20720 "-" "Mozilla/4.0 (Windows XP 5.1)
Java/1.5.0_02"

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