Well, it could mean that your ISP is blocking that address, or the block of addresses it comes from. If you're running Windows you can try doing a traceroute and see whether or not that succeeds. You need to open a 'Command prompt' window though. The command is:
tracert 66.240.152.5
Here's an example of what you should get back, though the path from your PC won't be the same (hmm, interesting that RARP resolved the address to the name mail.oddesse.net): C:\Documents and Settings\Administrator>tracert 66.240.152.5
Tracing route to mail.oddesse.net [66.240.152.5] over a maximum of 30 hops:
1 25 ms 25 ms 25 ms L100.DSL-04.DLLSTX.verizon-gni.net [71.97.0.1] 2 25 ms 25 ms 24 ms P1-3.LCR-01.DLLSTX.verizon-gni.net [130.81.34.56] 3 27 ms 27 ms 26 ms so-6-0-0-0.PEER-RTR1.DFW80.verizon-gni.net [130.81.17.173] 4 27 ms 26 ms 26 ms dal-edge-11.inet.qwest.net [65.115.192.89] 5 26 ms 27 ms 25 ms dal-core-02.inet.qwest.net [205.171.25.149] 6 26 ms 25 ms 26 ms dap-brdr-01.inet.qwest.net [205.171.225.53] 7 27 ms 26 ms 26 ms qwest-gw.dlstx.ip.att.net [192.205.32.145] 8 61 ms 60 ms 60 ms tbr1-p012101.dlstx.ip.att.net [12.123.17.82] 9 59 ms 60 ms 61 ms tbr1-cl2.la2ca.ip.att.net [12.122.10.50] 10 57 ms 58 ms 57 ms gar2-p310.lsrca.ip.att.net [12.123.199.117] 11 58 ms 58 ms 58 ms 12.118.130.78 12 * * * Request timed out. 13 63 ms 59 ms 59 ms mail.oddesse.net [66.240.152.5]
Trace complete.
C:\Documents and Settings\Administrator>
If you look at that trace, you can see that my provider is Verizon. The trace goes through several of their routers before being handed off to QWest, which passes the trace through its network and on to AT&T, which passes it to a core router at 12.118.130.78 (which is programmed to not give out its name), which delivers the packet to the address I'm trying to trace.
If your ISP is blocking the address, then you'll probably only get one or two lines before you get a string of '* * * Request timed out' messages and a notice the trace failed.
Since the address resolves to mail.oddesse.net it would appear that somebody's using, or has previously used, that address for a mail server, in which case it could have been tagged as a spammer at some point.