The globus-crft --concurrent option only takes effect if info->block_size is
also set, and I don't see a command-line option for setting info->block_size. 
It looks like a test for (info->block_size > 0) was inserted by mistake. 
Here's a patch:

Index: globus_crft.c
===================================================================
RCS file:
/home/globdev/CVS/globus-packages/ws-transfer/reliable/client/c/crft_util/source/globus_crft.c,v
retrieving revision 1.8
diff -u -r1.8 globus_crft.c
--- globus_crft.c    15 May 2006 20:03:13 -0000    1.8
+++ globus_crft.c    8 Nov 2006 16:22:55 -0000
@@ -307,7 +307,6 @@
         *info->input.choice_value.value.transferRequest.allOrNone =
             info->all_or_none;
     }
-    if(info->block_size > 0)
     if(info->concurrency > 0)
     {
         xsd_int_init(