Please publish a complete schematic of what you are doing. I gather the last one is based on a dual rail configuration, so it's not very helpful to diagnosis!
Also it would be good to know what these "class A" op amps are---input bias currents in particular, tendency to polarity reversal when common-mode range exceeded, etc.
The major problem with single supply stuff is the assumption that a simple bypassed voltage divider behaves the same way as a hard ground in a dual rail config. If you pull hardly any current it's a good assumption. If you start loading it a bunch, look out.