First of all, make sure that you have the geom_stripe kernel module loaded. It could be loaded automatically by gstripe label, but lost during reboot.
If not, it may be a probe ordering issue. I am not sure where gvinum stores its metadata. If in the beginning of the disk, then result can be unpredictable. You may try to use gmirror instead of gvinum to create RAID1s. Also you may use graid to create a single RAID10 volume.