thin measuring lines

Hi,

I haven't been using Graffle for a long time and so far been editing old files, so please excuse me if this is a really stupid question.
Today I've begun creating new files with OG 5.2.2, and at once I ran across a really odd thing. Distances between objects seem to be calculated automatically and shown in thin blue lines. One thing is that as far as I can see the values are not correct and another is that objects seem to want to align along those thin blue lines. This conflicts with my standard grid. What are those lines and where can I switch them off/on? Right now I only want the grid.
I used an empty template to which I added a standard grid with automatic alignment and *metric* units, 1cm with 5 subdivision lines. 
(I wish that Omni added the possibility to choose unit systems to the general prefs in the Graffle menu. For a continental European like me there is no point at all in any other unit systems, and having to use a special template in order to avoid having to switch to metric units every time I create a new file is a bit unnatural.)

Marion