Readstring()

You might need to show your code and the file.
Using the WriteString example from B3D...

; Reading and writing a file using ReadString$ and WriteString functions

; Initialise some variables for the example
String1$ = "A short string"
String2$ = "A longer string since these are variables lengths"
String3$ = "This is string3 "
String4$ = "joined to string4"

; Open a file to write to
fileout = WriteFile("mydata.dat")

; Write the information to the file
WriteString( fileout, String1 )
WriteString( fileout, String2 )
WriteString( fileout, String3 + String4)
WriteString( fileout, "Just to show you don't have to use variables" )

; Close the file
CloseFile( fileout )

and then this in Bmax...

mystream:TStream=OpenStream("mydata.dat")
While Not Eof(mystream)
	Print ReadLine(mystream)
Wend

works OK.