Error Code 505, proxy, Mail, DNS . . .

Question

No broadband where I live; wireless out of reach of my budget; so stuck with slow-as-cold-molasses dial up.  My telephone company and isp techies say 4.5 kbs is pretty much as good as it gets speedwise.  Can you imagine, those of you who are racing across cyberspace at 200kbs and faster?  Maybe jetting at megabytes, for all I know!
My Mac is a Mini desktop: OS X 10.6.2   Safari 4.0.3   (tried to download upgrade but would take nearly 3 days & after 8+ hours--I did try for the heck of it--it timed out with 1 day and 23 hours left).
Recently switched to high speed dialup; worked better than I expected, so long as I don't mind image disintegration at the high settings.   I even started using Mac's Mail rather than isp's email client and worked flawlessly.   Until recently . . . a bunch of issues cropped up nearly all at once and seems related.
No. 1:  MAIL fails to FORWARD messages with GRAPHICS.  After a minute of trying, up pops message:  server not accepting username & password, check to see if correct or choose another server from list (the list shows my other mail boxes all under same principal username and password).   Erratic behavior: sometimes emails with graphics do get forwarded, and then for two or three days the glitch is back & cannot forward. 
No. 2:  Mac and/or Safari keeps changing proxy setting back to Mac's default.  My isp says to uncheck all proxies, leave all blank.  When I do this, no trouble accessing internet. It is irritating when so often I get online okay but message comes up Safari could not access server; so I have to get off-line, go into Sys Preferences, unlock, and uncheck the proxy setting that Mac checked again, apply change (again) and lock (again) which is useless since in spite of locking Mac still changes proxy back to what it wants it to be.  Mac does this when I boot up after computer has been shut down.  But not every time.  Sometimes I can get online without a browser glitch.   This Macintosh is starting to behave as badly as my old PC.
No. 3:  Most recently, past few days, the locked proxy setting has held, but at the same time another, new problem.  The isp's high speed function is failing to be activated and the message I get when booting up is:   OS X network settings could not be integrated with server.  Error Code 505.   The browser works but files are not being compressed & it's the old molasses speed.
I searched my computer and got several files, all programming jargon of course, showing this info: 
1)  library if true    */
          kCGLGOUseErrorHandler  = 505,          /* Call the Core Graphics handler on CGL errors  */
2)  /* 505 */EXTERN void                    Tcl_RegisterConfig (Tcl_Interp* interp, CONST char* pkgName, Tcl_Config* configuration,
                                        CONST char* valEncoding);
#endif
#ifndef Tcl_CreateNamespace_TCL_DECLARED
#define Tcl_CreateNamespace_TCL_DECLARED
3)  Slot 505 is reserved
My isp's support technician is apparently a PC man and does not know Mac to troubleshoot. 
One more thing: the DNS settings also change.  Sometimes there is nothing, just blank; other times I see one domain address or another.  I thought this was supposed to be my isp's DNS which was put in automatically at setting up (downloading) the isp's software and should stay the same. 
Any help would be much appreciated.
Thanks.
Donna 

Answer 1

Think you going to have to have someone get your data off and reinstall your operating system, update your machine to 10.6.8 etc. Get you working again.
Changing DNS is a security issue. Stop all online banking and other credit card transactions, check your accounts.
Try to find DSL service at least. Your phone company usually offers something.