There is a bug in upstream linux (introduced in 2.6.25.6 and fixed in 2.6.26) which prevent booting any TSC-less machine (and thus any 486-based machine, like the net4501).
Upstream commit fixing this is df17b1d990fc214f033c5588e58216ec941591e0
Cherry-picking this commit onto hardened-sources-2.6.25-11 and rebuilding the kernel fixed my 1.8.3 installation

(from redmine: issue id 44, created on 2009-06-17, closed on 2009-10-09)