Hi man,
wassssuppp ?
i think i found the issue here...
i'm running SU6 and i found 2 issues:
1.Sketchup didn't recognize my path to the folder...
or that it was unable to read my file name (i had some files in Latin language)...
solution:
create a "tmp" folder under drive (i.e. "C:\my_dwg") and export the file (DWG) to there (give it a simple name like "try")and import to sketchup from there.

2. when i've created some dwg files i insert unsupported charecters to the Layer Manager... i.e. i had layer which called "table&carpet" or ".door"
   and ONLY after removed those illegle charecters sketchup was able to load it ...

hope i'ved help u...
let me know if i didn't and will try to figure something for u.
Shto