so far i've tried with .tar and .zip files
No problem here with xarchiver version 0.4.3svn-r23781 I created a new zip archive in my home directory, dragged a few files from Thunar to xarchiver, closed xarchiver and opened the zip file again with xarchiver and the files were there.
well the latest version does not work. at least when you drop the file to the treeview. when you drop it on the toolbar for example, it works.
Just updated to r23798. Works fine.
what version of gtk do you have? i have 2.10.6 here.
I have 2.8.19
The faulty code, causing the signal drag_data_received not to to be emitted, is the notebook creation at src/interface.c lines from 340 to 348. We sent an email to the gtk-app-devel list to find out why.
Fixed in r23892.