No, I did not have any error.Quote from PhanxYou're almost certainly getting an error. Install Bugger (or at least turn on the default UI's option to show errors, under Interface > Help, though it can't show errors that happen during the loading process) and then go post a bug report to the plugin's author with the error.
If the plugin is no longer maintained, you're probably out of luck, sorry. The raid sizes in WoD are just not the same as the raid sizes in MoP, and I don't intend to write a whole compatibility layer to trick old plugins into thinking we're still in MoP.
It was not a problem of other sub-addon as well. I disabled all sub-addons of Grid, but the problem stayed.
The problem was in some misinterpretation by Grid of previously saved settings. I began to play with various sizes and parameters, and succeeded to bring the situation to almost identical as it was with the previous (release) version of Grid.
So now I actually don't have the problem which I complained about.