I've upgraded to EE2.7.3 and CT 2.5 now when I go to Cartthrob > Settings > Payments I'm getting a grey screen and all navigation is disabled (have to click back button to get out). Is anyone else experiencing this or know of a fix. Display Output Profiler and Template Debug not outputting anything either.
I had a similar issue with CartThrob 2.7.1 on EE 2.11.2 - the Modules : Payments setting page wasn't loading past the EE header and displaying a memory error at the foot of the source HTML.
The solution involved removing all gateway php files in /system/expressionengine/third_party/cartthrob/payment_gateways/ except Cartthrob_payment_gateway.php and the gateway(s) you require - e.g. Cartthrob_paypal_express.php