* i unknown the specific problem, but try this ( have a 65000 limit )
CLEAR
lcMyString = "!!aaa!bbb!!ccc!!ddd!eee!!"
? m.lcMyString
PRIVATE aParsing
for lnI = 1 to ALINES(aParsing, m.lcMyString+" ","!!")
     lnStart = AT( '!', aParsing[m.lnI])
     IF m.lnStart>0
       aParsing[m.lnI] = STUFF(aParsing[m.lnI],m.lnStart,1,"DO")
     ENDIF
ENDFOR
IF m.lnI > 1
	lcMyString = aParsing[1]
	FOR lnI = 2 TO m.lnI-2
		lcMyString = m.lcMyString + "!!" + aParsing[m.lnI]
	ENDFOR
	lcMyString = m.lcMyString + "!!" ;
				+ IIF(aParsing[m.lnI]==" ","",LEFT(aParsing[m.lnI],LEN(aParsing[m.lnI])-1))
ENDIF
? m.lcMyString