From my personal experience, the whole PSN has been acting weird all weekend. I got a lot of PSN errors and disconnects. Might have something to do with it.
This appears to be happening more frequently when PD is working on something. When Photo Stream started, several people would lose tire sounds when playing online, myself included.
I'm willing to bet it's a by-product of GT Academy development, but until someone here gets a job with PD, we'll never actually know.
You can mitigate your liabilities.
1. Make sure you have a hardwired connection directly to your modem, and reset your modem before playing. Skip routers, go straight to the source.
2. Sync your clock and trophies. My theory is that it improves the "handshake" with PD servers, but for all I know it just pokes the demon inside the PS3. I don't really care, because it's been reported to work.
3. Clear your system cache. If you remote race a lot, play online, or do tons of Seasonal Events, it clogs up the tubes. Unclog your tubes, man.
4. If you've enabled, and are playing custom music soundtracks, stop. Disable custom music. It's been known to cause problems way back when, and to my knowledge was never officially addressed. Happy to be proven wrong here.
5. If possible, avoid using mics. There's a known glitch (pre-2.05, if I'm right) when there are too many wheels and mics in use. Count on others using wheels, and just disable mics.
6. Before you go online, save your progress. It doesn't hurt.