  Virtual quark pair screening leads to breaking of the string between
fundamental representation quarks in QCD. For unquenched four dimensional
lattice QCD, this (so far elusive) phenomenon is studied using the recently
developed truncated determinant algorithm (TDA). The dynamical configurations
were generated on an Athlon 650 MHz PC. Quark eigenmodes up to 420 MeV are
included exactly in these TDA studies performed at low quark mass on large
coarse (but O($a^2$) improved) lattices. A study of Wilson line correlators in
Coulomb gauge extracted from an ensemble of 1000 two-flavor dynamical
configurations reveals evidence for flattening of the string tension at
distances R $\geq$ approximately 1 fm.
