Crash while downloading server stuff

[degausser]

I'm a long-time-gone member of this awesome community trying to return to it on my new iMac. Apparently all the downloads I need to play HL2RP are downloaded via Gmod itself now, so that's cool. You used to have to navigate all sorts of websites of questionable repute to get the server downloads. However, and I've tried this several times, every time I open Gmod, select the HL2RP server and the server downloads start, it gets stuck on "models/props/smallcubetrt.vvd" and then Gmod crashes or "unexpectedly quits". Anybody have any idea why this is happening? I'm not Lua or programming savvy at all, but any advice would be greatly appreciated.
My specs:
OS X Yosemite V10.10.1
27" iMac
3.4GHz Intel Core i5 processor
8 GB 1600 MHz DDR3 RAM
NVIDIA GeForce GTX 780M w/ 4.096 GB VRAM

EDIT
I watched it more closely this time, it actually got past the previously mentioned download and crashed on "materials/gui/ad2logo.tga". Thanks for your time if you're reading this.

UPDATE
Tried deleting HL2/ep1/ep2/gmod, and redownloading in that order, still crashes on the same download. No idea why.

 

[Artemis]

I've noted even with all the content packs it's that material or the turtle thing (don't have the exact path on me at the moment) that don't crash me, but take much longer than they should to 'download' and this 'download' happens every time I join the server no matter how much I do, slowing down my connection every time I transition or anything really.