Well see, its weird because as long as I never save my work it is fine. Let me explain... when I start a new route, I can work for as long as I want and place even large amounts of the highest poly rolling stock I can get my hands on, and it won't lag. It can also be a completely empty map. But as soon as I have saved it, regardless of whats on the map, the framerate instantly drops down to almost 1 fps. This is not remedied by leaving the game and opening it again, or accessing the map in driver and then coming back to surveyor. Driver mode on the route does, however, run perfectly smoothly (unless there is alot of high-poly rolling stock in the frame, but that's normal).
I turned off all nonessential programs, but I can't disable my internet connection. I'm not sure I understand why the internet being plugged in matters at all...
This sounds like a problem with your hard disk, and not the program. Once you start writing to the drive, the writing is continuing while you attempt to do other things. The constant "chattering" of your drive is stealing CPU and I/O cycles away from the program, so the program now stutters and has a low frame rate.
There are many that can cause this including low disk space, a highly fragmented hard drive, and both a very plugged drive that was never defragmented.
So when was the last time you did a little housekeeping on your computer?
Clean-up old temporary files, archive any unneeded documents and pictures to archival media, remove and unused programs, and then defrag your drive. This can make a big difference in the performance of your system.
Your antivirus program can cause things like this.
If your AV program is scanning every save, then it will continue to scan the data and again steal CPU and I/O cycles from your program. To remedy this problem, I have excluded my Trainz Local folders from real-time scanning. This doesn't mean I don't scan for malware, it just means I don't scan the folder all the time. There is probably some risk here, but overall I've been lucky with Trainz related content. I run a daily scan of the data drive, and have never found any viruses.
One of the biggest culprits I have found is Windows Indexer and Windows Search. If you installed MS Office 2007, and in particular Outlook 2007, then there's a big fat possibility that Windows Search has been disabled. Turn this off, and your system will act better.
What is happening is every time you save a file, Windows Search kicks in to update its database of file locations so you can find something a microsecond faster than you could without it.
Instead of speeding things up, it slows everything down because the drive is busy all the time as the data is being read. This can be disabled in the Control Panel. Go to Admin Tools and then Services. Look for Windows Search, and stop it and disable the service. Outlook may complain about it, but just click the check box not to show you the message again.
If your drive is very full, this can also cause saving and writing problems. A full drive is like a room or closet full of boxes. You can only fit just so much, and if you do have some space, it's difficult to get to, so Windows will do a little swapping, removing its own temp files, etc. to make enough space to fit the file. The disk will continue to write and slow up your system while Windows is working at this.
John