ISA 2006 Web Proxy filter - 12006 The URL does not use a recognized protocol

Hi,

I have a ISA 2006 server running web proxy filter and encountered a situation where the server would return the following error for every Proxy request it receives:

12006 The Uniform Resource Locator (URL) does not use a recognized protocol. Either the protocol is not supported or the request was not typed correctly. Confirm that a valid protocol is in use (for example, HTTP for a Web request)

I could not get any proper information about this error and why it would occur.
Now it's important to understand that this could not be a configuration problem, the server is actually running and working and continued to work after restarting ISA. what I saw is that before the errors started to rise, the ISA server was restarted but it seems that it simply did not load properly. I'm getting a very bad mixture of messages in the Application event log right after it loaded and started having the problem:

Event Type: Error
Event Source: Microsoft Firewall
Event Category: None
Event ID: 14018
Date: 26/08/2010
Time: 02:12:09
User: N/A
Computer: PROXY5
Description:
ISA Server failed to load the firewall policy configuration.


Event Type: Warning
Event Source: Microsoft ISA Server Web Proxy
Event Category: None
Event ID: 23005
Date: 26/08/2010
Time: 02:12:09
User: N/A
Computer: PROXY5
Description:
The compression settings in the stored ISA Server configuration are not valid and could not be loaded by the Compression Filter because the following error occurred: Not enough storage is available to process this command.
.
To fix this problem, open ISA Server Management, expand the General node, select Define HTTP Compression Preferences, and enter valid configuration settings for compression.


Event Type: Error
Event Source: ISA Action
Event Category: None
Event ID: 0
Date: 26/08/2010
Time: 02:12:09
User: N/A
Computer: PROXY5
Description:
Error in ISA action!
Exception from HRESULT: 0xC0040393.


Event Type: Error
Event Source: Microsoft Firewall
Event Category: None
Event ID: 14057
Date: 26/08/2010
Time: 03:56:59
User: N/A
Computer: PROXY5
Description:
The Firewall service stopped because an application filter module C:\WINDOWS\system32\kernel32.dll generated an exception code E06D7363 in address 77E4BEF7 when function CompleteAsyncIO was called. To resolve this error, remove recently installed application filters and restart the service.


Well, all these errors are not really nice, but the one that strikes me most is the second one. the thing is, I had the same server return Error 502 to users a couple days ago with the following error:
HTTP/1.1 502 Proxy Error ( Not enough storage is available to process this command. )
As you can see the syntax is identical. but the "Not enough storage" error exists on the Internet endlessly, for example:
http://service1.symantec.com/SUPPORT/sunset-c2002kb.nsf/0/4187fcd0a0ade53585256edd00478e67?OpenDocument
The server does in fact have Symantec AV installed.

However, this document, or any other one I found regarding this error, does not have any relation to ISA Server so I'm not sure it's even remotely connected. obviously disk space and RAM are ok on the machine so it's not a straight-forward "storage space" problem. there is a 5.8Gb Swap space. and also, ISA has a cache drive of 1Gb.

I investigated all possible leads that I could think of and came up with nothing. it would be grealy appreciated to get any inputs here. Thanks