A lot of questions about Visual FoxPro 6.0 are cropping up on the message board here. To set things to rest: Web Connection works fine with VFP 6.0, but there are a few things that you need to do:
RECOMPILE EVERYTHING You have to recompile all code! This is because VFP 6.0 includes some functions that are in Web Connection's libraries natively now. The main ones are all of the FoxTools functions. Because of the way VFP 6.0 uses a 5.0 compiled code and the way Web Connection sets the version flags code using any of the duplicated functions will cause problems unless you recompile.
SET STRICTDATE VFP 6.0 has a new SET STRICTDATE command that does not allow ambigous date syntax. If SET STRICTDATE is left at its default you may have problems with your existing code that uses dates. wcMain that ships with Web Connection turns off STRICTDATE in the startup code to avoid this. If you're updating you may not be doing this and thus see these problems. Use the following code somewhere in your startup code to turn off STRICTDATE logic. Otherwise be prepared to hunt down ambigous dates.
#IF wwVFPVersion > 5
SET STRICTDATE TO 0
SET CENTURY OFF
#ENDIF
Personally I prefer to use SET CENTURY ROLLOVER 80 to avoid the whole Y2K issue.