firefox-3.5.6 text rendering

[fulvio ciriaco <oivulf%gmail.com@localhost>]

Hallo,
I have a problem with firefox-3.5.6 (from repository),
the problem happens after some usage and consists
of missing characters in the text with spaces in their
place. Reload does not affect it but restarting brings back
all the text. So, some kind of degradation seems to be happening.
$(uname -a)=NetBSD fulvio 5.99.22 NetBSD 5.99.22 (GENERIC) #0: Wed Dec  9 
04:23:36 UTC 2009  
builds%b8.netbsd.org@localhost:/home/builds/ab/HEAD/i386/200912090000Z-obj/home/builds/ab/HEAD/src/sys/arch/i386/compile/GENERIC
 i386
All dependancies are from the repository 5.0.1_2009Q3 and uptodate according
to pkgin.
Fulvio