Hi guys, I have a technical problem with the core wallet, can anyone help?

I have been using version 0.11.0 for a while now, and it was working fine, but recently it started showing "this version is obsolete; upgrade required!", and as a result I couldn't send any transaction since.

I sent a couple test transfers to my friends, they showed up in the list, but never went through - they have just been sitting there unconfirmed for a couple of days now.

Recently, however, the "this version is obsolete; upgrade required!" notification has disappeared, but the transactions still can't reach their destination. What should I do?

One thing I should mention is that I have quite a lot of money on that wallet, so I absolutely cannot fuck this up.