oscam dropping cards after a few hours

Running a Ubuntu 11.04 server with auto install cccam/oscam (213/updated oscam to 6192)
installed omnikey drivers and edited lines-

remove hash from 'try_emulation_first = yes;'
remove hash from 'lock_login = true;' and change value to false?

2 omnikey readers with setanta and viasat

all connected ok and in oscam cards are showing entitlements fine,connects fine to cccam and clears setanta sports etc on hop 1.

This lasts for about an hour or so and then the cards drop out (still showing all entitlements ok) and i have to re-insert them into the readers for the channels to clear on hop 1.

configs are-

[reader]
label = slyuk
protocol = pcsc
device = 0
caid = 0963
detect = cd
mhz = 480
cardmhz = 357
ident = 0963:000000
group = 1
emmcache = 1,3,2

[reader]
label = viasat
protocol = pcsc
device = 1
caid = 093E,090F
boxid = ********
detect = cd
mhz = 357
cardmhz = 357
ident = 093E:000000;090F:000000
group = 2
emmcache = 1,3,2

[account]
user = blahblah
pwd = blahblah
group = 1
monlevel = 0
au = ***uk
caid = 0963
keepalive = 1

[account]
user = blahblah
pwd = blahblah
group = 2
monlevel = 0
au = viasat
caid = 093E,090F
ident = 093E:000000;090F:000000
keepalive = 1

[global]
logfile = /dev/null
cachedelay = 120
nice = -1
preferlocalcards = 1

[monitor]
hideclient_to = 15
appendchaninfo = 0

[newcamd]
port = *****@0963:000000;*****@093E:000000,090F:000000
key = 0102030405060708091011121314

[webif]
httpport = 8888
httpuser = blahblah
httppwd = blahblah
httprefresh = 5
httpallowed = 127.0.0.1,192.168.0.0-255.255.255.255

ports, box id's and usernames/passwords have been changed.

anybody see any problems or does it all look fine?
Or any other suggestions as to what the problem could be?

Update- i have disabled the check scripts and still the same.
so i tried doing one thing at a time- removed omnikey reader with viasat card and just ran setanta in the other omnikey reader.
removed user account and line in cccam.

now when i go onto setanta sports 1 my local card opens but only for a few mins(1 or 2 at best) then reverts to my peer(hop 2)

any suggestions???

doing my head in now :(

Update, I was about to give in and swap to Debian but decided to try one last thing.
I removed the powered usb and plugged the Omnikey direct into the server(still only running one reader with Setanta)
and it has appeared to cure the problem,I haven't added the other Omnikey with Viasat yet,but all looks to be stable (left it over the weekend).