General :: Content Of Variable Crashes VBA Code

I have a form I use to create photo captions. The form has a field where users can edit a pre-generated caption and a field that stores their updates as a final caption in the field "selected_caption".. On my form is a button that runs the code below to check and see if a field ("updated") has been marked true, then copies the content of caption field into the selected_caption field. It works fine 90 percent of the time but for some reason this caption:

LA 109535, LA109535 partial site overview showing blowout with PL's 01- 04. Crew person is excavating a shovel test probe. Photo direction facing southwest. (Roll 31066, Frame 4958)

Results in a missing operator error. I thought it was like a special character thing, so I removed the "'" and the "-". Same error.

Code:
Dim db As Database
Dim rst As Recordset
Dim upcap As String
Dim strSQL As String
Set db = CurrentDb

[Code] .....