So I've created a fair few EE sites before but never come across this issue, recently installed EE on a mediatemple grid host and all seemed to be working fine until I created multiple channels, some of the channels are refusing to output any content at all where as others will output content fine, using the most basic of code so there's definetly no issues in the actual template code.
Any ideas as to how I could go about fixing or debugging this?
Turn on template debugging and the output profiler in Admin > System Administration > Output and Debugging. Reading through those logs should give you a very clear idea of what's stopping your channels from rendering content.