Can anyone help with problem number one please (I have two problems)... Clematis?

[Marthaclematis]

Hi there, I have a lovely clematis which is four years old, never had any problem with it until this year. It grew up lovely and healthy until the first flower buds came... They are all being eaten, by some invisible force, from the tip down. One is half eaten and the other has its tip just starting to be decimated. There are no teeth marks or anything, no insects I can see. Its horrible, each bud, as soon as its ready to open, gets gobbled. Its never happened before, nothing else is being attacked. The iris in close proximity are nearly open. The rose with buds look ok. Does anyone know what it might be and what I can do ? Many thanks.xx

[rustylady]

Snails??? I have thousands of the bu@@ers at the moment, they're thriving in all this rain. Pop out and have a look - this is about the time they start munching.

[Marthaclematis]

mmmmm... dunno. I will have a look. I hope it IS snails, I can deal with those and as it gets higher up the fence the blighters should be left behind. We put some nemaslug in two nights ago. I know that they don't 'do' so well for snails but maybe it will help a bit.
Its just the way the flowers are 'eaten' - really cleanly, like they've been sliced cm x cm with a knife. No marks.