IE7 loses connection to SOME sites

Hello,

Until one/two months ago, my Vista machine was working perfectly. Suddenly
the machine started loosing its ability to access SOME web pages with IE7, to
download emails with Windows Mail, and to update SOME of the software
installed. The only way to get it to work again is to restart the machine.
Then, the Internet will be fine for 2~6 hours and the IE7 losses the access
to SOME (NOT ALL) sites again.

During these periods of “faulty Internet access� I CAN ping and tracert web
sites I cannot access with IE. Some sites, randomly, can even be accessed by
IE. Vista network connection is presented as Internet.

Since I have not installed new software and malwares have not infected the
machine, I tried to narrow down the possibilities. Removed AV and Firewall
software and performed a clean boot. Nothing. My Internet connection still
dropping every 4 hours or so.

I have a Motorola 5101i Cable Modem, a RT31P2 Linksys VoIP router and a
WRT54G Linksys wireless router. If I connect directly to the Cable Modem, the
problem remains. Lease time for the WRT54G is 24 hours. I have tried to use
fixed IP and DHCP in both routers, wireless and wired connections, connect to
the RT31P2, and the problem remains.

Just one more thing, a XP machine does not face any problem using the same
network.

Thanks in advance.
Mauricio

Follows a capture with Microsoft Network Monitor 3.1 when the problem occurs.

Frame:
- WiFi: [Encrypted Data] F....E, (I)
- MetaData:
Version: 2 (0x2)
Length: 32 (0x20)
- OpMode: Extensible Station Mode
StationMode: (...............................0) Not Station
Mode
APMode: (..............................0.) Not AP Mode
ExtensibleStationMode: (.............................1..) Extensible
Station Mode
Unused: (.0000000000000000000000000000...)
MonitorMode: (0...............................) Monitor Mode
Flags: 0 (0x0)
PhyType: Undefined Value (0)
Channel: 9
lRSSI: -34 dBm
Rate: 54 Mbps
TimeStamp: 09/08/2008, 09:27:18
- FrameControl: F....E (0x0842)
Version: (..............00) 0
Type: (............10..) Data
SubType: (........0000....) Data
DS: (......10........) DS to STA via AP
MoreFrag: (.....0..........) No
Retransmission: (....0...........) No
PowerMgt: (...0............) Active Mode
MoreData: (..0.............) No
Encrypted: (.1..............) Yes
Order: (0...............) Unordered
- Data:
Duration: 44 (0x2C)
+ APToClient:
- WiFiPayload:
WMM:
- LLC: Unnumbered(U) Frame, Command Frame, SSAP = SNAP(Sub-Network Access
Protocol), DSAP = SNAP(Sub-Network Access Protocol)
- DSAP: SNAP(Sub-Network Access Protocol), Individual DSAP
Address: (1010101.) SNAP(Sub-Network Access Protocol)
IG: (.......0) Individual Address
- SSAP: SNAP(Sub-Network Access Protocol), Command
Address: (1010101.) SNAP(Sub-Network Access Protocol)
CR: (.......0) Command Frame
- Unnumbered: UI - Unnumbered Information
MMM: (000.....) 0
PF: (...0....) Poll Bit - No Response Solicited
MM: (....00..)
Type: (......11) Unnumbered(U) Frame
- Snap: EtherType = Internet IP (IPv4), OrgCode = XEROX CORPORATION
OrganizationCode: XEROX CORPORATION, 0(0x0000)
EtherType: Internet IP (IPv4), 2048(0x0800)
- Ipv4: Next Protocol = TCP, Packet ID = 0, Total IP Length = 40
- Versions: IPv4, Internet Protocol; Header Length = 20
Version: (0100....) IPv4, Internet Protocol
HeaderLength: (....0101) 20 bytes (0x5)
- DifferentiatedServicesField: DSCP: 0, ECN: 0
DSCP: (000000..) Differentiated services codepoint 0
ECT: (......0.) ECN-Capable Transport not set
CE: (.......0) ECN-CE not set
TotalLength: 40 (0x28)
Identification: 0 (0x0)
- FragmentFlags: 16384 (0x4000)
Reserved: (0...............)
DF: (.1..............) Do not fragment
MF: (..0.............) This is the last fragment
Offset: (...0000000000000) 0
TimeToLive: 57 (0x39)
NextProtocol: TCP, 6(0x6)
Checksum: 44784 (0xAEF0)
SourceAddress: 200.98.249.120
DestinationAddress: 192.160.16.100
- Tcp: Flags=..R....., SrcPort=HTTP(80), DstPort=50596, Len=0,
Seq=2628929521, Ack=0, Win=0 (scale factor not found)
SrcPort: HTTP(80)
DstPort: 50596
SequenceNumber: 2628929521 (0x9CB247F1)
AcknowledgementNumber: 0 (0x0)
- DataOffset: 80 (0x50)
DataOffset: (0101....) (20 bytes)
Reserved: (....000.)
NS: (.......0) Nonce Sum not significant
- Flags: ..R.....
CWR: (0.......) CWR not significant
ECE: (.0......) ECN-Echo not significant
Urgent: (..0.....) Not Urgent Data
Ack: (...0....) Acknowledgement field not significant
Push: (....0...) No Push Function
Reset: (.....1..) Reset
Syn: (......0.) Not Synchronize sequence numbers
Fin: (.......0) Not End of data
Window: 0 (scale factor not found)
Checksum: 29288 (0x7268)
UrgentPointer: 0 (0x0)