DNN log shows
d:\Inetpub\vhosts\(domain)\httpdocs\DesktopModules\YetAnotherForumDotNet\pages\admin\users.ascx(191): error CS0104: 'Config' is an ambiguous reference between 'YAF.Configuration.Config' and 'DotNetNuke.Common.Utilities.Config'

Same in line 213 of users.ascx
Solved by changing "Config.IsDotNetNuke" to "YAF.Configuration.Config.IsDotNetNuke"

DNN log shows
d:\Inetpub\vhosts\(domain)\httpdocs\DesktopModules\YetAnotherForumDotNet\pages\admin\users.ascx(191): error CS0104: 'Config' is an ambiguous reference between 'YAF.Configuration.Config' and 'DotNetNuke.Common.Utilities.Config'

Same in line 213 of users.ascx
Solved by changing "Config.IsDotNetNuke" to "YAF.Configuration.Config.IsDotNetNuke"

Thanks, issue will be fixed in the next release