[TxMt] How to switch off the Shift+Option+S combination?

Hello,

I have modified my keyboard (Dvorak, if that matters) to produce the following combinations:

Option + C -> č Shift+Option+C -> Č Option+S -> š Shift+Option+S -> Š (and some more).

This all works wonderful everywhere, except that Shift+Option+S in TextMate results in something like cat: /tmp/TextMate-ScratchSnippet.txt: No such file or directory The same actually happens when pressing that combination on US layout (except that probably not many TextMate users ever need to type "Í" on it) and no other key is problematic, only S.

My question is: where to turn that non-working feature off (Shift+Option+S), so that I will be able to use that key combination to get my character?

Thanks a lot, Mojca