Google picks and chooses meta descriptions

Did we do something to offend them?

[stugre]

Since what might have been termed a slightly more dramatic "rolling" change to the SERPS over the last couple of weeks (I'm hesitant to call it an update) it seems Google is taking an interesting approach to meta descriptions in the KW's that I monitor.

For some sites nothing has changed - the meta description entered is being used as that nice little snippet of text under the link in the SERPS which makes everything nice and easy for those webmasters.

For us, it's become a nightmare as Google refuses to recognise we have a meta description all of a sudden and seems to be going out of its way to pick up the most non-sensical sections of text which, when combined, appear to be doing nothing but putting visitors OFF visiting our site.

Any ideas would be greatefully received, I've been tinkwering with the index copy but to no avail, Google just moves the goalposts...