oPreview is losing scope and destroying the form. Make oPreview a property on the form that contains the Preview button and change the code to look something like

ThisForm.oPreview = Createobject('CRYSTALPREVIEW',myReport,MyString)

>Hello All!!
>Ok Here's the deal.
>I have this form that I have made a crystal viewer. It is a class all by it self
>I pass it the Name and parameter string (if there are any) and here is what happens:
>
>When I run it at the command line, Everything is fine ie.
>
>

>mystring = 'previous=15459.60;Company=61;Crop Year=2002;Commodity=ROUGHRICE;Class=LONG;asofdate=04/07/2003;Pool=AR;Uom=CWT;'
>myReport = 'C:\riceland2k3\viewstockrecorderp\output\stkRec001b.rpt'
>oPreview = Createobject('CRYSTALPREVIEW',myReport,MyString)
>

>
>This peace of code runs the form and it is previewed fine in the screen,
>however, When I call this class from a button on a form, It just flashes and goes away.
>
>

>&&Here is the code That makes the string, and calls the class
>mystring = [previous=]+myprevious+[;]
>mystring = mystring + [Company=]+ALLTRIM(thisform.txtcompany.Value)+[;]
>myString = mystring + [Crop Year=]+ALLTRIM(thisform.txtcropYear.Value) + [;]
>myString = mystring + [Commodity=]+ALLTRIM(thisform.cbocommodity.value) + [;]
>myString = mystring + [Class=]+ALLTRIM(thisform.cboclass.value) + [;]
>myString = mystring + [asofdate=]+ALLTRIM(DTOC(thisform.txtasofdate.value)) + [;]
>myString = mystring + [Pool=]+ALLTRIM(thisform.cboPool.value) + [;]
>myString = mystring + [Uom=]+ALLTRIM(thisform.cboUom.value) + [;]
>
>&& Keep in mind that myString Is the Exact same thing as the mystring above
>
>MyReport = 'C:\riceland2k3\ViewStockrecordERP\OUTPUT\stkrec001b.rpt'
>MyPreview = CREATEOBJECT("CRYSTALPREVIEW",myReport,MyString)
>

>
>When that code runs, it just flash and leaves.
>What could I be doing wrong?
>If you need the code in my Preview form I can post it as well
>
>Thanks in advance