Description
Unfortunately, some code inside SharePoint 2010 uses the for (var x in seq) pattern for enumerating arrays. If we include the Script# library in such a page, the SharePoint code will break because methods added to the prototype of arrays gets enumerated as well.
Of course, the perfect solution would be to have the SharePoint code fixed, but that's hardly an easy thing to do, and anyway I'd have to support customers who didn't install the fix.
To me, another option would be for Script# to stop depending on array prototype extensions, and instead use a global function (or something else, this really doesn't matter).
We've had this issue for a while (long before the code was published), and we ended up implementing such a change both in mscorlib.js and in the compiler IL code (I know, I shouldn't do that, but it was instructive). Of course now I cannot easily upgrade.
Now that the source is available (didn't knew that, it's great!), I might re-implement this change and submit a pull request, but in the coming weeks I don't expect to have much time for this.