I have seen a similar problem; occasionally, the game will hang when I am trying to load into a MystCraft age, and then after I load, I will be at my spawn, with no items. To avoid this, what I've started doing is a "test travel" to a new MystCraft age, before I go there for real. I generally just put all my awesome gear into a chest, grab only a Linking Book back home, and then try the new age. If I get through, I know the age is "safe", and then I'll go back with my gear. If I don't, then I know the age is "corrupt" and I don't lose anything except a linking book when I respawn, empty handed, at the original overworld spawn.
This has basically solved the issue for me, but I've never had it be an issue except for the actual crash occurring as I traveled between worlds. So, I'm not sure how useful this strategy will be for you. I also noticed that if I craft four or five linking books, I think it somehow confuses Minecraft - I've started just doing one book at a time, then traveling to it to ensure that it works, and then doing the next. Maybe something about having multiple, untraveled ages is causing a problem?
Side note: I kind of "handwaved" the freezing and lost inventory away as being a side effect of traveling to ages (so, in character, sometimes when you try and travel, you wake up naked outside, unsuccessful). Heh, so now I just treat it as a feature, not a bug. :P
Once you have the base Sphax texturepack downloaded, you have to grab the Sphax for FTB addon from the same site. Note that the addon supports Mindcrack, DW20, Lite, Tech World, and Magic World FTB packs, but not Ultimate. If you're playing Ultimate, Sphax is not (yet) the texturepack for you.
Best Answer
The Technic pack includes Optifine, which has support for HD Textures included. Try installing the technic pack first over a vanilla (un-modded, un-changed) version of minecraft. Then put the texture pack in
C:\Users\yourname\Appdata\Roaming\.minecraft\texturepacks(on Windows), you can also type%APPDATA%in the address bar in windows explorer and navigate to.minecraft\texturepacks.If this does not work try following the instructions in the "If you have previously used MCPatcher" section of this Minecraft Forum post.