Hi Christopher,
Not sure I understand the first question. DT-Ints doesn't use any of the timers by it self so they are free for you to use which way you see fit.

The 18F4550 has three external interrupt pins (not counting IOC) and these are PortB.0-PortB.2. Only these three pins can trip an interrupt. So if what you're really trying to do is to trip an interrupt on PortB.5 it will never work. (Actually PortB.5 has the IOC features so it CAN work but it doesn't appear like that's what you're doing).

Without seeing the rest of your code, with the interrupt declarations ets it looks to me like you're triggering an interrupt on INT0 (PortB.0). When it fires it checks PortB.5 and if it's logoc low you're jumping to RECEIVING_DATA. Using a GOTO to jump out of an interrupt service routine is generally a VERY bad idea because the program execution will then not reach the @ INT_RETURN which is a very bad thing indeed.

One more thing. IF you're doing this in an effort to receive RS232 data using SERIN or SERIN2 it won't work. I won't elaborate more on that in case that's not what you're doing.

/Henrik.