VS12 possible a/c change 14th June?

Just logged on to check our seat assignments on our return flight from Boston. For months the seat map has shown fine (A340-600) and our seats in PE reserved, but now it says:
Boston to London, Sat 14 Jun, 19:45
We're sorry. The seat map is not available at this time. Your seats will be assigned at check in.
Any ideas? Remembering prior threads does this generally mean VS may switch the a/c at the last minute?

Cheers
James

[honey lamb]

It could also mean that the number of seats available for pre-allocation has been reached and that the rest will be assigned at the airport.

If you go into the manage my booking page and click on the arrow beside your name a drop-down menu should confirm your seat booking still exists

On our website it's still showing as an A340-600. Think it will stay on this a/c as loads are full at the front and in premium and only 21 spare in economy. Very much doubt it will change to a 340-300, especially with G-VSUN's return delayed.
Think honeylamb is right and the pre-allocation limit has been reached.

Originally posted by honey lamb
It could also mean that the number of seats available for pre-allocation has been reached and that the rest will be assigned at the airport.

If you go into the manage my booking page and click on the arrow beside your name a drop-down menu should confirm your seat booking still exists

Thanks for that - HL you were right, I hadn't noticed that our original seat assigments still show against our names! That'll teach me [8D]

Cheers
Jamees