When I enable debug mode by setting the necessary system property, Scalr bails out due to a NullPointerException.

This is caused by line 148 in Scalr.java:

static {
    log(0, null, "Debug output ENABLED");
}

Since the second param (message) is null, the call to System.out.printf(message, params) throws an exception.
It looks like that line should read

log(0, "Debug output ENABLED");

anyway...