problems entering and exiting kde

I have SUSE 8.0 on Athlon 1600 xp, 256 MB ram, Matrox G550. I have two problems: 1) Sometimes it takes very long time (even 2 min.) for kde to start after startx command, both as root or normal user. 2) When I issue the command to exit kde to go back to the command line the screen turns black, the hard disk stop and everything seems to be dead (no response to ctrl-alt-bksp either). I have to reset. Any idea ? Thanks a lot. Riccardo, Italy.