nope, not over yet

if i have opened the program 'terminal' and type 'htop' , program is opened
is see, cpu/mem/swp on the left side above. memory is very low, sometimes 100 from 1009 available memory.
swap is 0, but sometimes the cpu goes to 100%, this is when a new page is loaded in midori, but i guess that is normal.
when i have closed all the programs and watch only htop, i see sometimes that the cpu rockets to 100%.
when i watch all the command lines in htop is see under the column 'ni' that all is '0' , except for the line;
/sbin/udevd -d
i have this line 3 times and they all have negative numbers, like -4 and -2 and -2
should these lines have negative numbers ?
Edit; when i was typing this, htop was already stopped working, uptime 15.30minutes. i could still type here but had to make another hard reset. all was stalled. something very curious..............
Willem