A few more ideas for the the possibie fonts issues -you could clean the font and other caches e.g. with OnyX (it's free). Just select the 10.4 PPC version http://www.macupdate.com/app/mac/11582/onyx
You could also test for the fonts issue by disabling all fonts except system fonts in Font Book app. If after disabling them, and logging off and back in on your Mac, if the browsers still behave as previously, then we'll know it's not the fonts. But it might well be them.
If the issue disappears with added fonts off, enable 50 % of them and see if it occurs, again limiting to the 50 % of the sample to identify the bad ones.
You could also test for the fonts issue by disabling all fonts except system fonts in Font Book app. If after disabling them, and logging off and back in on your Mac, if the browsers still behave as previously, then we'll know it's not the fonts. But it might well be them.
If the issue disappears with added fonts off, enable 50 % of them and see if it occurs, again limiting to the 50 % of the sample to identify the bad ones.