Monitor (Dell E228WFPc) will not detect Ubuntu (12.04) computer once switched away from and then back to on KVM switch (Rosewill RKV-4UC).

I have three computers hooked up to a KVM switch (Rosewill RKV-4UC) so that they all share the same monitor (Dell E228WFPc). Two of the computers run Ubuntu 12.04, and the other one runs Windows 7. When I switch the monitor away from either one of the Ubuntu machines, and then cycle back to that same machine, the monitor no longer picks up a signal from that machine, as if no computer was hooked up to it at all. I recently updated the two Ubuntu machines from 11.10 to 12.04, and I never experienced this issue with 11.10; as well, the Windows 7 machine does not produce this issue (that is, I can switch the monitor away from and back to the Windows 7 computer with no issue). So, this issue appears to have come with 12.04 (that is, it does not seem to be a direct fault of either the monitor or the KVM switch, but it appears to be directly related to the operating system). Any help or advice will be appreciated. Thank you.