Ok, I've found the problem: It is between the SCC API implementation on the Visual FoxPro side and SourceOfSite.
I've tested using the 30 days trial of SourceOfSite 5.0.3 from their web page (https://sourcegear.com/sos/downloads.html)


This is the log generated on VFP command window for a test form I made when I checkin a test form, and at the left I've added the step number on which this log is generated:

[ 3] * Source Control : Checking in c:\desa\sourcesafe\form1.scx...
[ 8] * Source Control : Checking In File: c:\desa\sourcesafe\form1.sca
[ 9] * Source Control : Retrieving File: c:\desa\sourcesafe\form1.scx
[10] * Source Control : Checking Out File: c:\desa\sourcesafe\form1.scx
[11] * Source Control : Retrieving File: c:\desa\sourcesafe\form1.sct
[12] * Source Control : Checking Out File: c:\desa\sourcesafe\form1.sct
[15] * Source Control : Checking In File: c:\desa\sourcesafe\form1.scx
[15] * Source Control : Checking In File: c:\desa\sourcesafe\form1.sct
[ ] * Source Control : Completed


This is what happen (the log explained) using a comment that have LESS than 64 characters:

1 - You checkout a form (form1.scx), change something on it, save and close de form (the icon is a red mark)
2 - Then you checkin the file from the VFP Project with right click-checkin and a windows appears in which you can enter the comments (less than 64 chars), and when you press "OK" start the process (and the log on VFP command window)
3 - VFP does a checkin of the scx/sct
4 - VFP ask the conversor the kind of support it have for this type of file (scx)
5 - FoxBin2Prg replies "bidirectional support" (note: Scctext replies "only text" at this point)
6 - VFP ask the conversor for the generation of the text file
7 - Then FoxBin2Prg generates the sca text from the binary
8 - VFP does the checkin of the sca text file and make it ReadOnly
9 - VFP ask SCCAPI that retrieve the scx binary file => The file is retrieved as ReadOnly
10 - VFP ask SCCAPI that checkout the scx file (to make it writable) => SourceOfSite make it writable
11 - VFP ask SCCAPI that retrieve the sct binary file => The file is retrieved as ReadOnly
12 - VFP ask SCCAPI that checkout the scx file (to make it writable) => SourceOfSite make it writable
13 - VFP ask the conversor to regenerate the binary
14 - Then FoxBin2Prg regenerates the binary from the sca text
15 - VFP does the checkin of the regenerated binaries (scx/sct) and make them ReadOnly
16 - VFP ask the conversor the kind of support it have for this type of file (scx, again)
17 - FoxBin2Prg replies "bidirectional support" (again)
18 - VFP updates the project window and show the blue padlock icon


And this is what happen when you do the same, but when using a comment that have MORE than 64 characters:

1 - You checkout a form (form1.scx), change something on it, save and close de form (the icon is a red mark)
2 - Then you checkin the file from the VFP Project with right click-checkin and a windows appears in which you can enter the comments (more than 64 chars), and when you press "OK" start the process (and the log on VFP command window)
3 - VFP does a checkin of the scx/sct
4 - VFP ask the conversor the kind of support it have for this type of file (scx)
5 - FoxBin2Prg replies "bidirectional support" (note: Scctext replies "only text" at this point)
6 - VFP ask the conversor for the generation of the text file
7 - Then FoxBin2Prg generates the sca text from the binary
8 - VFP does the checkin of the sca text file and make it ReadOnly
9 - VFP ask SCCAPI that retrieve the scx binary file => The file is retrieved as ReadOnly
10 - VFP ask SCCAPI that checkout the scx file (to make it writable) => SourceOfSite shows an error message "Operation failed $/test_proj/form1.scx"
11 - VFP ask SCCAPI that retrieve the sct binary file => The file is retrieved as ReadOnly
12 - VFP ask SCCAPI that checkout the scx file (to make it writable) => SourceOfSite shows an error message "Operation failed $/test_proj/form1.scx"
(at this point scx and sct are ReadOnly)
13 - VFP ask the conversor to regenerate the binary
14 - Then FoxBin2Prg try to regenerate the binary from the sca text, but can't because destination binary files are ReadOnly and this make FoxBin2Prg fail with "File access denied" message, and return an system level error code
15 - VFP ask SCCAPI a rollback of the files, ovewriting your changes with the last checked in versions

* I've made the same testing with SourceSafe VFP project integration, and it have not this problem when adding comments with more than 200 chars (as I said in the other post)

* I've repeated the checkin/checkout with SourceOfSite, but without the project integration, just from SoS GUI, and it works ok and you can add more than 64 characters

So, as you can see, this is not FoxBin2Prg problem. It have to do with some limitation between VFP and SourceOfSite integration involving the support of bidirectional convertion of files and all the processes that go behind.

I think you have 2 choices:
1) Don't use comments with more than 64 characters when checking in VFP binaries
2) If want to use more than 64 characters in comments for VFP binaries, then you can do it from SoS interface directly, and not from the integration with the VFP project, but in this case you must do the text generation with FoxBin2Prg from the File Explorer, before checkin in with SoS GUI.


Regards.-