ok when i extacted from some models using mesh extract, and then i merge the multiple polymsh_extracted i get a distortion of polygons
please help

Select all of your objects then click on the freeze button in the bottom right corner. If you're running a monitor resolution lower than 1280x1024 (I don't know why people would go lower) then you wont see it so just right click on the dark gray bars on the right panel to collapse them and then you should see it.

freezing the objects was my first solution but it dident work

@Mini: People could go lower because it's generally the default moniter size on non-LCD screens. And a lot fo moniters cant reach it, such as my second one.
When you merge mshes, are you going to teh explorer, hitting the plus sign next to your polymsh, then selecting merge meshes (you might have to hit another plus, referencing from memory at teh moment) (Merge meshes has a gear as its icon in the explorer) and then a window will pop up. Select merge UVs and such and then lower the tolerance to .01. That works, dunno if you did that.

Well then it is the settings, whenever you merge a dialogue box pops up to change things, like whether to merge materials and UV's, delete or hide the input meshes and most importantly the tolerance. The tolerance settings need to be set to 0, what this does is the calculates distance between vertexes and welds them based on how close they are to one another. If property editors do not show whenever you create a primitive or use a tool then go into your preferences and click on interaction and in the property editors/views tab make sure all but tab style property editors are checked and it should fix that.