So we saw this on an SBS 2003 R2 Premium machine that had been up for a long time. When we did some Googling we came across the following article which we figured would be required, http://www.taznetworks.com/rss/2006/01/sbs-backup-error-code-0x800710d8.html . Simple easy, with just a few server reboots.
When we examined the server more closely we discovered that it had the well known SQL memory issue that SBS seems to suffer from on the MS Firewall service. What happens here is that you see an sqlsever instance consuming a huge amount of RAM. When you look closer at the source of the instance you find it is the ISA 2004 reporting database. You can find more information about the solution to that here but basically you need to run the command line WMSDE tools to limit the amount of memory the WMSDE instance uses (WMSDE is the cut down version of SQL you get for free). So we did that since the server couldn't be rebooted and low and behold the backup the following day worked!
So it would seem that not only is the backup error 0x800710d8 potentially related to a corrupt RSM database but it is dependent on the memory in use on your server. So before you go recreating your RSM database try seeing whether your server maybe consuming an inordinate amount of RAM. If it is try throttling some of the SQL instances as detailed above or like most things, maybe a simple reboot to free up memory again will do the job.