My machine has 16 GB RAM and when analysing only 4 GB RAM are used including the OS (no other software running). Stockfish will use all the CPU-resources available (not RAM, that depends on the Hashtable-size) also when you use only one line. You probably mean to reduce the number of physical/virtual cores the engine is allowed to use. Reducing that does not help as well (and using all cores should not lead to freezes anyway).
Komodo or Fritz engine are running fine by the way. But I like Stockfish more (solves complex tactical positions faster from my experience).
Who else experiences micro-freezes (around 1-3 seconds) when analysing with Stockfish with multiple lines (I am using 4 lines at the same time, using only 1 line the problem does not occur) in one of the Chessbase GUIs (e.g. CB15-GUI, Fritz-GUI)? It seems the Chessbase GUI has some bug with the UCI protocoll or setting when connected to Stockfish...
The issue has been reported here, so I am at least not the only one having this problem (on two different machines with different hardware/software):
http://support.stockfishchess.org/discussions/problems/7978-stockfish-not-responding-when-analyzing-in-fritz