[X4U] 10.3.8 issues on powerbook

[alexandre]

hi.

i'm taking care of a friends titanium 550 (running 10.3.8), making sure 
it runs smoothly. lately he's been having some issues:

- it takes forever to boot.

- safari crashes, sometimes doesn't even open

- the computer won't wake from sleep.

what could be the cause of this? i've done the usual: verify 
permissions, run macjanitor, checked the disk, but nothing has come up. 
this friend shares this computer with his girlfriend and they often 
change the kanguage set up of the finder, from german to english and 
back. could this be a potential source of problems? to prevent this, 
i've now created two users, one in german and the other in english.

any info welcome¨
regards, alexandre