BLD:W0050
Expression "%s" contains path separator(s) "\/:" (not allowed here)
The indicated expression contains one or more path separators that are not allowed in this context. Although the expression expansion will succeed, the resulting value might not be valid for the context in which it is used and may cause the installation to fail.
For example, a shortcut's title may not contain path separators, because the title is used as a file name when the shortcut is created and embedded path separators will cause the shortcut creation to fail.
Solution
You should check the indicated expression and remove any path separators. Note that the path separators may occur in the expansion of expression rather than in expression itself. For example, if this message refers to the title of a shortcut that is set to <ProductName> and the ProductName variable is set to Ultrasoft/400, then the '/' in ProductName is the real culprit.