I'm having two likely related issues with Sky Blocks.

The first is that neither Sky Block is rendering correctly. Here is both regular and inverted blocks under the sun. Notice it doesn't show through on either.

Builds:
OpenBlocks-1.7.10-1.3-snapshot-450.jar
OpenModsLib-1.7.10-0.6-snapshot-230.jar

The second issue is a crash with just Inverted Sky Blocks. I'm hesitant to mention it at all because it appears fixed in today's build, but I'm including it just in case.

If you place the Inverted Sky Block, the game immediately crashes. It's a rendering bug, so it makes your world unplayable until you remove it with MCEdit. The regular Sky Block doesn't crash, but again isn't rendering correctly.

Crashlog: http://pastebin.com/7nXnHjPD

Builds:
OpenBlocks-1.7.10-1.3-snapshot-440
OpenModsLib-1.7.10-0.6-snapshot-227

Apologies if this is combining two separate issues into one, or if I shouldn't have mentioned the second at all - I'm just including in case it's relevant. I also didn't see anything about it in the changelog so I thought it might have not been known.

Both issues are caused by changes in Forge (more specifically, disabling of stencil buffers). In older version it caused crash (second issue, already fixed). In recent builds active skyblocks are just rendering as cubes in color of sky (they always were, but now extra process that made them look like sky is broken).

Normal skyblocks without redstone power and powered inverted ones are supposed to be rendered in disabled form (i.e. as block with dark clouds texture), so they are working as intended.