For play Open SP you should do normall install, mod activation (dont use there Open SP!), load updates with 'old' launcher, once use MP (reach main menu), restart CF, run CF again (this time with 'new' launcher, where click settings and tick checkbox 'OpenSP' and start SP.
Note: after install FL don't forget remove write protection!
And one more thing: in your Feelancer folder should be executable file OpenSPFix or similar ... you can try first use this one before do reinstall. (but that fix was needed before was released new launcher).