How to ignore .rnd files (permissions issue?)

[jeanadev]

As ack begins displaying search results this line will appear

ack: .rnd: cannot open file for reading

and then ack just hangs.

I added

--ignore-file=ext:rnd

to my .ackrc file, and I tried

--ignore-file=ext.rnd
--ignore-file=rnd 
--ignore-file=.rnd 

and I still get the

ack: .rnd: cannot open file for reading

message.

More info about the .rnd file...

ls -al .rnd
-rw-------  1 root  staff  1024 Sep 14  2011 .rnd

Any idea how I can successfully ignore this file?