Did you try drag-and-dropping the rings into the equipment window, as well as just clicking on them in your inventory?
Can you equip one ring, move it over to the left hand, then equip a second ring, or does the left hand cause a crash regardless of if there is anything in the right hand's slot?
Does the same thing happen in a new game? You should be able to run to Ars Magicana [optionally use
iZakaroN's SaveEditor (or from
Kiya's site, with description) to boost the character] and use a cheat to get enough gold to buy a couple rings from the mage Kistandalius;
<span class='standouttext'>Spoiler : </span><span class='spoiler'>To duplicate stackable items, such as gold or potions, drag a stack out of (or into) your inventory (or container) and hold down the control key before dropping. This will bring up the split stack pane; type in a negative number and hit enter (the checkmark will be greyed out). This can also be done in the trade window.</span> (highlight the text to read)
Troubleshooting Tips (& manual install procedure)