It stayed that way until I inherited it a few days ago and figured, I could try and remove it my self. I had nothing to loose. As it turns out, with a little patience, it's actually quite easy.
Step 1: Get your equipment ready
Step 2: Remove the glass gently
Using the long nose pliers, gently remove the glass from the filter ring.
Step 3: Bend the filter-ring back into shape.
Go around the filter and keep bending the filter back into shape until it actually loosens and it becomes possible to unscrew it.
Step 4: Clean your lense and you're done!
The entire thing took me little more than 15min and I ended up with minor scratches on the lense barrel but nothing seems bent and I’m sure that a new filter ring would fit perfectly on that lense.
Note, this wasn’t tested on plastic lenses. I’d be interested in hearing your comments.
Have a look at my flickr page