Many strange issues with 2009 Macbook Pro running 10.10.5 my wifes macbook pro started acting very strange this evening, and i can't seem to figure out what is wrong with it at all. here is a list of various issues that all seemingly started tonight:

ReportCrash using between 90 - 150% cpu

syslogd using over 150% cpu (although not at the same time as ReportCrash)

various programs not opening, including: mail, photos, preview, chrome, app store

very intermittent internet connection (via wi-fi) 

safari stating the certificate for google.com is not trusted

system crash, followed by kernal panic error message after restart

system crash during restart

spotlight search not showing applications in results, despite the option being ticked in preferences

various processes (not responding), including: steam helper, adobe creative cloud

(when trying to upgrade to el capitan) : el capitan upgrade asking for password to install, accepting password but not progressing, asking for password again, ad infinitum

"All My Files" folder showing no files.

etc, etc, etc

if this were a windows pc i might be able to figure it out, but i am new to OS X and this seems well beyond my understanding. thank you in advance for your help!!
My first guess would be a failing HD. You could try to look into the console.app, found here:

/Application/Utilities/Console.app


If the log shows IO-Errors it's time to replace the HD. 

There are of course other explanation, f.e. a corrupt Kernel extension or even a defective Font, but as i said it sounds like the HD.