My IXwebhosting account is saying a couple of my sites are hosted on sub domains rather than dedicated IP's Could this cause any problems with rankings or PR?
No, non-dedicated ip's won't affect rankings. Crosslinking your own sites with the same class "c" IP will not pass link juice as google assumes common ownership and the links are not "natural" votes. If you're running adsense on the sites, google knows about the connection regardless of hosting.