Hello scoco, welcome to the forum
A lot of people seem to have problems similar to yours with both Firewire and USB I think XP works better with these devices as it is a more "tolerant" OS than Windows 7 this is because Microsoft has tightened up the standards in an attempt to stop problems with drivers and devices.
I think your problems are caused by the devices but cannot rule out drivers. I would go as far as to say that the SIIG NN-EC2022-S1 may not be compatible with 7.
The Rosewill card on the other hand should work, but I am unsure what to understand by hot swapping. I would read that the card should be permanently plugged in and the fire wire devices can then be swapped as and when without switching off the OS.