Lets assume there is a smallest length (time), l_p, then at first glance, this appears to violate lorentz invariance, but it doesn't. Pretend there is some length operator
<br />
\hat{l_p}|l_p\rangle=l_p|l_p\rangle<br />
with fundamental length eigenvalue l_p. Then indeed this is the same regardless of the observer, but that is not a violation of lorentz invariance, because quantum tells us that quantity should not change from observer to observer, but rather the expectation value \langle l_p\rangle is an observer dependent quantity. And indeed the expectation value would vary from frame to frame.
Therefore if you treat the quantization of space-time, not only relativistically, but also quantum mechanically, there is no violation.