Cheshire Cat Computing

Is anyone successfully doing threshold checking with RRDtool 1.2.8 and MRTG 12.2.1? My setup was working fine with RRDTOOL 1.0.49 and an older version of MRTG. When I try RRDtool 1.2.8 on a test box it breaks the thresholding. Rolling back RRDtool to 1.0.49 fixes the problem. Running MRTG with --debug=log gives me this:

--log: Called: RRDs::tune(/opt/apache/htdocs/mrtg/target/target-cpu.rrd -a ds0:100 -a ds1:100 -d ds0:GAUGE -d ds1:GAUGE)
--log: Calling: RRDs::update(/opt/apache/htdocs/mrtg/target/target-cpu.rrd, '1119306448:13:13')
--log: Called: RRDs::last()
--log: Called: RRDs::fetch(/opt/apache/htdocs/mrtg/target/target-cpu.rrd,'AVERAGE','-s',1119306448,'-e',1119306448)
--log: got: NaN/NaN
WARNING: can't do threshold checking for target target-cpu(i) -- No valid current data
--log: Called: RRDs::tune(/opt/apache/htdocs/mrtg/target/target-mem.rrd -a ds0:512000000 -a ds1:512000000 -d ds0:GAUGE -d ds1:GAUGE)
--log: Calling: RRDs::update(/opt/apache/htdocs/mrtg/target/target-mem.rrd, '1119306448:1845136:4182248')
--log: Called: RRDs::last()
--log: Called: RRDs::fetch(/opt/apache/htdocs/mrtg/target/target-mem.rrd,'AVERAGE','-s',1119306448,'-e',1119306448)
--log: got: NaN/NaN