There are a couple of fixes to try listed below.
Select the Proper Object:
(I've been criticized for not using "proper" terminology here. I fully admit to not being a Blender expert or even particularly knowledgeable. These articles are just my own notes on what has worked to fix issues I've had. I put them here on my website so I can find them when I run into the problem again. If they help someone else as well, that's great!)
Open your model in Blender and go to "Object Mode" if you're not in it already. Select all (press “a” key) to highlight your entire Object. If it is selected an orange outline will appear around the Object perimeter. The Object selection is a toggle switch so press "a" again if your object is not highlighted.
Set Rotation & Scale:
Next, let's make sure the Rotation & Scale are correctly set. This isn't always necessary but it won't hurt so let's just take care of it while were here. Once again, be sure you are in "Object Mode." Now in the bottom menu of the 3d viewport select:
Object > Apply > Rotation & Scale.
Save your file. Now try exporting to Collada again using the SL settings. Often this simple solution will work.
If that doesn’t work you may need to rebuild the Blender ".blend" file. Rather than rewriting the instructions on how to do that, please see the instructions on the article on Blender crashing on Collada Export. That article goes through the process of rebuilding the .blend file.