Water flow/Lava flow bug

Sometimes,sometimes not, water and lava will incorrectly flow.

What I expected to happen was...:
Didn't EXPECT it, but to flow regularly.

What actually happened was...:
Pics explain.

Steps to Reproduce:
1. Make a box 3x3 and fill the inside edges with water bucket.
2. Dig in the middle 1-x blocks deep.
3. Put a block over the hole, not in it.
4. Remove the hole.
1b. Put down bucket (lava or water) on a flat surface. Won't work all the time. If it doesn't, try a DIFFERENT SPOT.