SharpDevelop form design don't work well after changed font

my os is Win7 home edition (chinese version). the system default font is “SimSun”.I use the sharpdevelop to write C# code (with net 2.0).

the form design work well with the default font (SimSun).

but after i change the form font to "Arial", it seems that the form design has some problems.

when I switch between "Source" page and "Design" page. the controls (buttons..) will become smaller and smaller.

( I capture some picture but i don't know how to insert pictures into the post。

If you need the pictures, please send me email(bisun112233@163.com). thanks.