Hi Flump,
I'm in exactly the same boat. Did 48:21 (a PB, hadn't raced a 10K for ages) at the beginning of the summer, after sporadic training. Really want to break 45min before I turn Veteran (eek!) in October. My next 2 10K's were both slower, despite having put in consistent training according to the RW 8-week 10K schedule. I've had really horrible stitches in my last 3 races, despite rarely getting them in training.
The training feels like it's going well, I enjoy the faster sessions, am comfortable on the longer runs, but it doesn't seem to come together for racing.
Incredibly frustrating. Keep us updated if things improve, I've got 25 days before my next race to try and turn it around.
Good luck!
Em