I've got this problem reading the skills of the TL1CP mod into the GUTS Skills Editor.

When I try to activate the Skills Editor, I get this...



It always stops at that point ("Loading 38/68"). 

The mod itself seems to be running fine, but I'm worried that this error is there in the first place 

I've tried reading through the error text from when you click the "Details" button to see if it might give me an idea of where to start looking, but it's hieroglyphics to me!

So I saved the error text to the attached file and I'm hoping some kind soul might be willing to take a look at it please?

...in some file you have a problem with the "Length" parameter, I suppose it is a syntax error.

I just did a string search through all .DAT files in the TL1CP media\skills folder - there is no incidence of the string "length"

I have another plan.
Delete all *.BINDAT files and start GUTS. After the error find all files that don`t have a BINDAT- pair.

Also did a search through all the .LAYOUT files, but nothing there either.

Am doing the .DAT to .BINDAT comparisons now...

EDIT:
No luck, all the .DATs have matching .BINDATs 

In addition, you can check a folder-by-folder.
Create special Test mod, and add 1 folder step-by-step from your mod. Each step checks GUTS for the error.

Doing a search on length won't find the issue.  It looks like it is treating strings as arrays. My guess would be either you have a field that is supposed to be filled in and is blank, or you have a field that has too much text in it.  My money would be on the empty field. I suppose it could be a field with a minimum length on it as well.

I'm not sure how much programming you've had, but basically "text" would be a string. You can treat it as an array of chars, and it would have a length property of 4.
You could then access each character in the array by its index. Most computer languages are zero indexed. So for my "text" example, it would be  "array[0]" and that should return "t", the first character. If nothing has been entered, and the program tries to read "array[0]", that is when you get the kind of error you uploaded earlier.

I hope that helps.

Based upon this:

   at System.String.InternalSubStringWithChecks(Int32 startIndex, Int32 length, Boolean fAlwaysCopy)
   at Editor.CDataBlock..ctor(String& data)
   at Editor.CDataBlock..ctor(String& data)
   at Editor.CDataBlock..ctor(String& data)
   at Editor.CDataFile..ctor(String filename)
   at Editor.SkillEditor.PopulateSkillList()

It's going to be an issue with the name or identifier of a skill.  I would suspect based upon the SubString, that it is expecting the identifier to be in a specific format.

EDIT:
After looking at a few dat files for skills,  I would check all those properties that have a colon in them. You may have accidentally typed a semi colon instead.

I agree with Vkoslak. It looks like it's trying to read past the end of a string.

An empty string is a strong candidate for being the cause.

A more subtle, and difficult to track down, possibility is that the empty string isn't in your file, but rather is a default for a mandatory field. GUTS very well might initialize mandatory string fields with empty strings (the default in C++), expecting them to be overwritten later with data read from the dat file. So you might look for missing or malformed lines for things like NAME that are possibly mandatory.

A third possibility is data corruption. Hard disks aren't perfect. A file that had nothing wrong with it when you saved it may have become corrupted in just the wrong spot. Unlikely, but it happens. (Happened to me once, in fact.)

You mean like NAME being mistyped as NMAE and similar? Yeah soooo many permutations. But I'll work along those lines as well

Yes, assuming my theories (that NAME is mandatory for skill dat files, and that mandatory string fields are initialized as an empty string waiting to be overwritten) are correct, then that is exactly the sort of thing that could cause this error.

Rather than searching for entries that are wrong, it might be easier to use a rule-out methodology. Use notepad++ to search for "<STRING>NAME:", "<STRING>DISPLAYNAME:", etc. across X files, until you find one that has less than X instances. Then start looking for the file with the typo.