CORE-9065 is not a suitable place for testing schannel, I opened new issue for this.
as I said in https://jira.reactos.org/browse/CORE-9065?focusedCommentId=72169&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-72169 ,
applying https://jira.reactos.org/secure/attachment/31780/schannel_sealunseal.diff makes ros schannel somewhat working in XP SP3.
However, ros schannel seems having issue with decrypting last part of message, which may be stalled or crashed.
regarding crashing/stalling, it happens in schan_DecryptMessage.
Windows XP SP3 stacktrace: http://pastebin.com/VUDHG1vg
the while loop need more love IMHO
(..\..\dll\win32\schannel\schannel_wine.c:1269) Received 1017728 bytes, data_size = 26
whole trace: http://pastebin.com/pV4BDQXL
and the stalling trace: http://pastebin.com/Bhmc0rvy