According to Gonzofts incredible work on how to get XTC to function with SX you always have to load pulsar effects through a MultiFX module. (I know it works without sometimes) Its something we just have to get used to, its not that difficult really.
Gonzofts Holy XTC Commandments:

"5. Always use the MultiFX modules when inserting more than one effect into channels in Cubase SX. Save the preset of the MultiFX, else Cubase won't remember the settings of the effects inserted into it the next time you open the program (SX). It seems that every host remembers only the settings of one instance below and effects inserted into the MultiFX are two instances below SX. "
The entire work can be read here:
http://www.planetz.com/forums/viewtopic ... 66&forum=3
Regarding more frequent crashes in XTC mode, I havent noticed this personally.
Happy XTC:ing

An eye for an eye, and soon the whole world is blind.
/Mahatma Gandhi