Log dir permissions - Blank Screen

[eluser]Pygon[/eluser]
This bug report is associated with a suggestion raised here:
http://ellislab.com/forums/viewthread/74377/
and the question posed here:
http://ellislab.com/forums/viewthread/71370/


Problem:
Incorrect permissions on the log directory causes system failure.

Expected Result:
Logging disabled, continue as normal.

Actual Result:
System failure, blank screen.

Testing Completed:
Function is_really_writable() works as expected.
Echo's prior to functions attempting to print to the log work.
Echo's after an attempt to print to the log fail.
Program logic seems to support the expected result.
-Unable to determine exact issue (just haven't have time to trace down a non-critical in my development)-