Well, none that i have personally experience.
Iv Fixed every single problem that has cropped up over the past 13 months for my 13 month old Install.
The 2 that took me the longest are both networking related.
At Boot up, the system would sit and wait doing nothing for up to a whole minute waiting for a network service to startup, once that service started all apps that relied on networking would complete loading, such as Samurize and the firewall, and actually youll be surprised just how many processes rely on the networking subsystem.
The 2nd problem was that i removed a broken NIC from my PC without first defaulting the setup and so the IP address remained locked to an on existent NIC also it was used for raspppoe and at the time i was using bridged mode ADSL and i was unable to get pppoe working until i found a way to disconnect the driver protocol fro mthe nic driver, i messed with the registry and got it working but windows XP no longer remembered drive letters for dynamic volumes when i rebooted (I don't see the relation but oookkk ) since then the old hdd that had a dynamic volume has broken down so if it happen again i doubt id bother to fix it.
I figured it out eventually and fixed that also, but windows networking never was the same, eventually i found out how to completely repair the damage instead of formating my windows partition and reinstalling, i wouldn't have a 13 month old xp install if i had formated then