Verizon, T-Mobile, and other services must interface with AT&T if they are to be interoperable. My phone is AT&T and I'm calling someone on Verizon. How does the signal pass from one to another? There must be "handshakes" between these separate systems in order for them to authenticate users through system ID and passwords. So, yeah, an architecture level system update could affect all these interactions. A classic Y2K-style unplanned hiccup.

Solar flare? Hogwash. Cover story? For what? Paranoid suspicion proves only that you have an overactive imagination and no substantiation. To borrow a phrase from Freud, "Sometimes a cigar is only a cigar."