where to start troubleshooting blank admin/orders.php

[SuperSewist]

admin/orders.php went blank this evening. I had made a small change to the html layout. Usually this means I goofed somewhere, so I reinstalled my backup while I worked on the new one as usual. Except the backup gives a blank screen, too. Well I've been down this path before, so went to the backup before I started this MOD. still blank. Went further back. no dice. Sent up the stock file, usually that fixes *anything*, but alas, still blank. Now I am stumped as to what to look for to find the problem. tsWebEditor says no prob in php. TIDY says no prob in html (ok, well none that matter - all those tables w/o summaries, y'know). All the other functions appear to be normal, I can get an invoice and packing slip by typing into the address bar. Customer list is fine. on the catalog side, all products show and ordering takes place properly. Anyone with a clue where I should be looking? What kinds of things I should look at? will post file code if requested. TIA

[SuperSewist]

This was a real pain to troubleshoot.

in admin/includes/languages/english/orders.php, I changed

define('ENTRY_CREDIT_CARD_NUMBER', 'Credit Card Number (last 4):');

to

define('ENTRY_CREDIT_CARD_NUMBER', 'Credit Card Number -last 4:');.

Why would this make a difference? Other define() have parens.

?????