nmap 3.75 vs 3.55

[micro dev <microdev1 () yahoo com>]

Hi,
nmap 3.75 shows problems for a subnet where nmap 3.55 works fine.
Here's initial output when scanned by 3.75 version and it never seemed to end....
 
nmap.exe -sS --max_rtt_timeout 300 --min_parallelism 50 -T 3 -O  -p 7,21,23,25,53,80,110,135,139,445,514,1066,1977 -v 
10.25.5.1-100
Starting nmap 3.75 ( http://www.insecure.org/nmap ) at 2005-01-21 09:34 Pacific
Standard Time
adjust_timeout: packet supposedly had rtt of 64188000 microseconds.  Ignoring time.
adjust_timeout: packet supposedly had rtt of 64188000 microseconds.  Ignoring time.
adjust_timeout: packet supposedly had rtt of 64188000 microseconds.  Ignoring time.
adjust_timeout: packet supposedly had rtt of 30000000 microseconds.  Ignoring time.
adjust_timeout: packet supposedly had rtt of 30015000 microseconds.  Ignoring time.
adjust_timeout: packet supposedly had rtt of 69000000 microseconds.  Ignoring time.
adjust_timeout: packet supposedly had rtt of 69000000 microseconds.  Ignoring time.
adjust_timeout: packet supposedly had rtt of 27000000 microseconds.  Ignoring time.
adjust_timeout: packet supposedly had rtt of 27000000 microseconds.  Ignoring time.
 
When scanned by 3.55 version, it works fine. Infact it took just 20 seconds to scan 100 IP addresses. Here's initial 
ouput  - 
nmap.exe -sS --max_rtt_timeout 300 --min_parallelism 50 -T 3 -O  -p 7,21,23,25,53,80,110,135,139,445,514,1066,1977 -v 
10.25.5.1-100

Starting nmap 3.55 ( http://www.insecure.org/nmap ) at 2005-01-21 09:58 Pacific Standard Time
Host 10.25.5.1 appears to be up ... good.
Initiating SYN Stealth Scan against 10.25.5.1 at 09:58
Adding open port 139/tcp
Adding open port 135/tcp
Adding open port 53/tcp
Adding open port 445/tcp
The SYN Stealth Scan took 0 seconds to scan 13 ports.
For OSScan assuming that port 53 is open and port 7 is closed and neither are firewalled
Interesting ports on 10.25.5.1:
PORT     STATE  SERVICE
7/tcp    closed echo
21/tcp   closed ftp
23/tcp   closed telnet
25/tcp   closed smtp
53/tcp   open   domain
80/tcp   closed http
110/tcp  closed pop3
135/tcp  open   msrpc
139/tcp  open   netbios-ssn
445/tcp  open   microsoft-ds
514/tcp  closed shell
1066/tcp closed unknown
1977/tcp closed unknown
Device type: general purpose
Running: Microsoft Windows 2003/.NET|NT/2K/XP
OS details: Microsoft Windows Server 2003 or XP SP2
TCP Sequence Prediction: Class=truly random
                         Difficulty=9999999 (Good luck!)
IPID Sequence Generation: Incremental

 
nmap 3.75 seems to be faster than 3.55 where it works but I have noticed that it fails in quite a few subnets.
 
Any ideas, why this happens ?
 
Thanks
 

                
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