It will not affect system stability, but... Surge protectors do not work at all without a ground wire to drop excess voltage to. Any kind of line voltage disturbance could kill every device.
Additionally, without any ground wire to pull the housings of devices to ground, the potential for a short to energize the case and then electrocute you is also high.
additionally additionally, if you have grounded outlets that don't actually have a ground connection running to them, that means either the wiring system is broken or it was "updated" by an unlicensed hack job who has undoubtedly made numerous more dangerous decisions elsewhere in the circuit.
If your house is entirely ungrounded you really should have an electrician come update it ASAP. Outlet grounds have been mandatory since 1971. The chances are high that wiring predating that code is still using old cloth-wrapped wire insulation or even knob&tube, both of which are huge fire risks as the insulation is decayed badly by now. It's expensive to have all new wire pulled but it is necessary.