Bosch SMS9022 dishwasher getting stuck at start of cycle

[PaulOckenden]

The dishwasher seems to be getting stuck on the initial phase of the cycle. From what I can hear, it's pumping out, and at the same time letting a bit of water in (the inlet valve opens). It nearly always seems to happen if I use the pre-rinse cycle, but also sometimes on the wash programmes.

It ISN'T the anti-flood kicking in - I've checked and the bottom is bone dry, the float isn't stuck, and the microswitch is working fine.

Anyone got any other ideas what this could be?

Thanks a million,

Paul.