problems with LTM serial connection to Raritan Dominion SX II

We converted our remote console access devices from Cyclades (which worked great) to Raritan Dominion SX II systems and I can't get many of the LTMs to work properly. I have a Viprion 2400 pair and a 6900 pair working fine, but our 8900, 3600 and 1600's won't stay connected. I get garbage on the screen and can't get any proper response on the console. All console settings are default (19200 8,N,1). Anyone seen this before or have any ideas on a solution? Thanks.