problem with xterm and RELENG_5

Hello,

recently shells from xterm stopped showing up in 'w' :

M ~ [12930] > w
 5:57PM  up  5:02, 1 user, load averages: 0.07, 0.20, 0.17
USER             TTY      FROM              LOGIN_at_  IDLE WHAT
arno             v0       -                12:56PM  5:00 xinit
M ~ [12931] > ps ux | fgrep xterm
arno 10150  0.0  0.2  1608 1016  pa  S+    5:58PM   0:00.00 fgrep xterm
arno  2049  0.0  0.6  5144 4084  pb  S+    3:39PM   0:01.21 xterm -geometry 80x
arno  2050  0.0  0.6  5144 4084  pb  S+    3:39PM   0:01.06 xterm -geometry 80x
arno  2051  0.0  0.6  5144 4084  pb  S+    3:39PM   0:01.17 xterm -geometry 80x
arno  2060  0.0  0.6  5144 4084  pb  S+    3:39PM   0:01.20 xterm -geometry 80x
arno  2061  0.0  0.6  5144 4084  pb  S+    3:39PM   0:01.45 xterm -geometry 80x
arno  2063  0.0  0.6  5144 4084  pb  S+    3:39PM   0:01.25 xterm -geometry 80x
arno  3255  0.0  0.6  5144 4084  pi  S     5:02PM   0:00.50 xterm -geometry 80x
arno   963  0.0  0.7  5696 4484  v0  S    12:56PM   0:03.40 xterm -geometry 80x
arno   965  0.0  0.7  5692 4720  v0  S    12:57PM   0:01.86 xterm -sb -sl 2038 
arno   991  0.0  0.8  5696 4724  v0  S    12:58PM   0:02.46 xterm -geometry 80x
arno   993  0.0  0.8  5700 4792  v0  S    12:59PM   0:04.06 xterm -geometry 80x
arno   998  0.0  0.7  5352 4380  v0  S    12:59PM   0:01.74 xterm -T handig -e 
arno  1001  0.0  0.8  5696 4724  v0  S    12:59PM   0:03.20 xterm -geometry 80x
arno  1025  0.0  0.7  5692 4720  v0  S     1:03PM   0:01.80 xterm -sb -sl 2038 
arno  1049  0.0  0.7  5696 4636  v0  S     1:14PM   0:01.91 xterm -geometry 80x
arno  1080  0.0  0.7  5692 4632  v0  S     1:28PM   0:01.66 xterm -sb -sl 2038 
arno  1105  0.0  0.7  5696 4636  v0  S     1:39PM   0:06.82 xterm -geometry 80x
arno  1110  0.0  0.7  5696 4636  v0  S     1:40PM   0:01.90 xterm -geometry 80x
arno  1346  0.0  0.7  5692 4632  v0  S     3:07PM   0:01.36 xterm -sb -sl 2038 
arno  1393  0.0  0.7  5692 4632  v0  S     3:07PM   0:01.53 xterm -sb -sl 2038 
arno  1527  0.0  0.7  5700 4704  v0  S     3:27PM   0:01.49 xterm -geometry 80x
arno  2166  0.0  0.7  5696 4636  v0  S     3:44PM   0:01.57 xterm -geometry 80x
arno  5192  0.0  0.7  5692 4632  v0  S     5:51PM   0:00.19 xterm -sb -sl 2038 
M ~ [12932] > 

so some are assigned to a new pseudo-terminal, others stay at v0.
gnome-terminal works OK;
downgrading to e.g. xterm-1.94 doesnt help

Regards, Arno