[xwiki-users] Can't add users to groups anymore after update from XWiki Enterprise1.9 to 2.0 and XAR reimport

Dear All, Since I updated from XWiki Enterprise1.9 to 2.0.3.24848, I can't add users to user-defined groups anymore. The new users are still assigned to the default XWikiAllGroup. I had made an XAR from my 1.9 Xwiki space to save some changes I made, which I imported again after updating. (Incidentally, the Xwiki Rights, Xwiki Global Rights, Xwiki Stylesheet Extension Class, XWiki Comment Class, XWiki Skin Class and the Javascript Extension Class pages in the XWiki space show errors when I look at them -- the exception: Failed to execute macro: velocity). I fear that something went wrong when I reimported the old Xwiki space. The rights seem to be affected with users having privileges which they shouldn't have according to the rights settings. Could someone please explain if any changes have been made to the macros on these pages from version 1.9 to 2.0? If so, would it be possible to print the xwiki editor content (where the velocity macros reside) in this forum so that the content could be compared? An XWiki 2.0 space XAR would be fine too. Then these old pages could be saved under other names, and only these 2.0 documents would be selected, imported and I could compare them. Any help someone can offer on these matters would be greatly appreciated. Thanks. Greetings, Steven Calkins