gtk-sharp-2.8.2 attempts to download from http://go-mono.com/sources/${PN}-2.0/${P}.tar.gz which fails. The 2.0 in the SRC_URI should be 2.8. Emerging a gtk-sharp component such as gnomevfs-sharp downloads gtk-sharp-2.8.2.tar.gz from the correct location.
Oy. Indeed. Fixed in CVS. Thanks for the report. Marking this FIXED.