Lyn, your profile does not say which build you are running 32-bit or 64-bit ?
You issues are most likely due to AMD/ATI Graphics. The R7 A8 series are quite low on the list at passmark.
[url]http://www.videocardbenchmark.net/video_lookup.php?gpu=Radeon+R7+A8-7600&id=3007[/url]
Currently SketchUp 2015 32-bit runs better, and crashes less, with AMD/ATI cards.
(It seems their 64-bit drivers may have issues with OpenGL.)