I've been getting frequent random crashes with version 0.6.4 (in the FTB Unstable pack). According to the crash report, it has something to do with the spreaders, but it happens when I'm out in the wild.

try without optifine. I'm starting to notice a pattern with it appearing in every crash report of this kind

@williewillus you should also probably just check that the alfportal isn't air. (inbetween here)

and such for all similar crashes.

if it's possible to fix it without alienating people whose computers only run modded with OF, it probably makes sense to do so.

I'm getting the same traceback without Optifine. It seems to be happening when I get around 10-12 chunks (Manhattan distance) from my Botania stuff (a few spreaders, mana pools, petal apothecary, runic altar, early flowers, and an inactive Alfheim portal). Crashes on client side only; server is fine.

    UCHIJA  mcp{9.19} [Minecraft Coder Pack] (minecraft.jar) 
    UCHIJA  FML{8.0.99.99} [Forge Mod Loader] (forge-1.8.9-11.15.1.1764.jar) 
    UCHIJA  Forge{11.15.1.1764} [Minecraft Forge] (forge-1.8.9-11.15.1.1764.jar) 
    UCHIJA  OpenComputers|Core{1.5.22.6} [OpenComputers (Core)] (minecraft.jar) 
    UCHIJA  Baubles{1.1.3.0} [Baubles] (Baubles-1.8.9-1.1.3.0.jar) 
    UCHIJA  Botania{r1.8-250} [Botania] (Botania.r1.8-unofficial-0.6.4.jar) 
    UCHIJA  chiselsandbits{mc1.8.9-v1.8.11} [Chisels & Bits] (chiselsandbits-mc1.8.9-v1.8.11.jar) 
    UCHIJA  inventorytweaks{1.60-beta-39-eae6253} [Inventory Tweaks] (InventoryTweaks-1.60-beta-39.jar) 
    UCHIJA  IronChest{6.0.125.770} [Iron Chest] (ironchest-1.8.9-6.0.125.770.jar) 
    UCHIJA  JEI{2.28.6.173} [Just Enough Items] (jei_1.8.9-2.28.6.173.jar) 
    UCHIJA  journeymap{1.8.9-5.1.5} [JourneyMap] (journeymap-1.8.9-5.1.5-unlimited.jar) 
    UCHIJA  OpenComputers{1.5.22.6} [OpenComputers] (OpenComputers-MC1.8.9-1.5.22.6.jar) 
    UCHIJA  Psi{beta-19} [Psi] (Psi-beta-19.jar) 
    Loaded coremods (and transformers): 
FMLPlugin (InventoryTweaks-1.60-beta-39.jar)
  invtweaks.forge.asm.ContainerTransformer
TransformerLoader (OpenComputers-MC1.8.9-1.5.22.6.jar)
  li.cil.oc.common.asm.ClassTransformer

that seems like a relatively innocent list. This seems like a chunkloading issue, such as we've had in the past.

I'm also getting "Ticking Block Entity" Crashes when i leave my Botania area.
this has been both on Mana Spreaders & Mana pools
I don't have Optifine installed (too many glitches in the render)
I'm also not using any chunkloaders.

1st report -
crash-2016-03-07_12.12.46-client.txt

2nd report -
crash-2016-03-07_12.24.34-client.txt

I can post a pic of my setup if needed.

Edit: just to note Air blocks seems to be involved in all these.

it's probably less that its air and more that the chunks are unloaded.