I've faced a similar issue, found that the Window's autotuning and omnirc were the issues.
Example:
#netsh int tcp show global
Querying active state...
TCP Global Parameters
----------------------------------------------
Receive-Side Scaling State : enabled
Chimney Offload State : automatic
NetDMA State : enabled
Direct Cache Acess (DCA) : disabled
Receive Window Auto-Tuning Level : normal
Add-On Congestion Control Provider : ctcp
ECN Capability : disabled
RFC 1323 Timestamps : disabled
#C:\>netsh interface tcp set global autotuninglevel=disabled
Ok.
#C:\>netsh interface tcp set global rss=disabled
Ok.
C:\>netsh int tcp show global
Querying active state...
TCP Global Parameters
----------------------------------------------
Receive-Side Scaling State : disabled
Chimney Offload State : automatic
NetDMA State : enabled
Direct Cache Acess (DCA) : disabled
Receive Window Auto-Tuning Level : disabled
Add-On Congestion Control Provider : ctcp
ECN Capability : disabled
RFC 1323 Timestamps : disabled
Also added the following to my omnirc
OB2IPCKEEPALIVE=1
OB2IPCKEEPALIVETIME=900
OB2IPCKEEPALIVEINTERVAL=50
OB2IPCNOSENDRECVLOOP=1
OB2RECONNECT_RETRY=3600
OB2RECONNECT_ACK=7200
OB2SHMIPC=0