OK I have deleted the skeleton part of the ParticleSystem and that now works fine, thanks.
There is still the same error with the weaponset, it says AddConditionFlags is an unknown field. So, is there a particular place in the INI, in which this weaponset upgrade must go? As this was the problem earlier. At the moment the actual Weaponset is under the standard weaponsets and the WeaponSetUpgrade is right at the bottom with the rest of the Ring Code (see above).
Here's the new weaponset upgrade (I made sure that I changed the weaponset to correspond with the new condition too):
Behavior = WeaponSetUpgrade ModuleTag_RingWeapon TriggeredBy = Upgrade_UseRing AddConditionFlags = WEAPONSET_CREATE_A_HERO_WS_01 End