I'm not that technically savvy when comes to SMS technology, but I can hardly imagine this being a problem on Android's end. It sounds to me like telco's problem. Could also be related to your connection. When SMS can't reach you, telco has an automated re-send feature, which keep sending the message till it finally reach you. This auto loop last for up to 24 hours, after which the interval become longer. At least that's how it works here (telcos in Malaysia). If the phone is in and out of connection, you might end up getting multiple copies of the same message.
I would suggest getting in touch with your provider, they might need to reset your account and the fact that it happens along your update, could simply be coincidental.