Bad rectangle dimensions

I have new user with SketchUp. I use the sw for a week, and something went wrong today. I planned a lot of basic shapes, and with the rectangle tool I made sqaures via dimensions write in. It worked properly till the evening. At the evening I used the program, and if I gave a dimensions for a square, for egsample, 40, 40 (mm), the program will not do it. It makes random sizes squares, if I measure with measurement tool, it will not the size, that I input in the dimensions.
It looks like totally random sizes, but only one size, the other one is sometimes 40mm, sometimes 40.4 mm.
I have no idee how it is possible, but if I give 40 to a round, it will be perfect. It looks like the square function is damaged.
Any idee?

It sounds like you aren’t entering the dimensions correctly. Exactly what are you typing in the Measurements box for the dimensions? Do you normally use a period or a comma for a decimal separator?

If your locale uses a full-stop [kka a point = . ] as its decimal separator, then
40,40 with no space
should work.
If you are in a locale where the decimal point is a comma [,] then the separator between the two entered dimensions needs to be a semi-colon [;] NT a comma [,] - otherwise that comma could clash with any decimal separator…
So try also

Also don’t click on the Measurements input box [aka the VCB]… just type values, clicking the box with mess up.

Thank you very much the problem was that I’ve tried the “,” and not the “;”. It works now properly.