have you been rebooting your servers?
my miners have been disconnecting and reconnecting.
you might want to consider a us based vps as a stratum server with ddos protection.

by the way I'm throwing over 100 mh at your servers....
it figures as soon at I get on your pool your ltc profits drop to 95% - arggh!
Give me 1-2 hours I start DDos VPS in USA.
About disconnecting - debug this problem now.