We present a series of monitoring observations of the ultrasoft broad-line Seyfert galaxy RE J2248-511 with XMM-Newton. Previous X-ray observations showed a transition from a very soft state to a harder state five years later. We find that the ultrasoft X-ray excess has re-emerged, yet there is no change in the hard power-law. Reflection models with a reflection fraction of ⩾15, and Comptonisation models with two components of different temperatures and optical depths (kT 1 =83 keV, T 1 =30 eV, τ 1 =0.8; KT 2 =3.5 keV, T 2 =60 eV, τ 2 =2.8) can be fit to the spectrum, but cannot be constrained. The best representation of the spectrum is a model consisting of two blackbodies (kT 1 =0.09±0.01 keV, kT 2 =0.21±0.03 keV) plus a power-law (Γ=1.8±0.08). We also present simultaneous optical and infrared data showing that the optical spectral slope also changes dramatically on timescales of years. If the optical to X-ray flux comes primarily from a Comptonised accretion disk we obtain estimates for the black hole mass ∼108M˙⊙, accretion rate ∼0.8M˙Edd and inclination cos(i)⩾0.8 of the disk.