SQL statements through JDBC causing QPSRVDMP's

Not exactly sure where to go with this so I'll start here on Midrange...

I have an application that uses JDBC to connect to a database. This app is DB agnostic (AFAICT). I created a collection/table on the System i using interactive SQL to manually enter the statements to create the DB. I am using jt400.jar to connect. All seemed well.

The actual internals of the program, the actual SQL statements sent over the wire, are not known to me. The app itself takes care of generating the SQL and retrieving the results. The application was EXTREMELY slow using the jt400.jar and when I switched to a MySQL JDBC connection, things speeded up with sub-second response times. Curious as to what was happening, I switched back to the jt400.jar and watched the connections using WRKODBCJOB (Bryan Dietz's great utility). It was interesting as connections were briefly made, then disappeared. Made, then disappeared. I managed to view the job log of one of the connections while it was in transit and saw the following:

Attributes of value number 5 in field HVR0005 not valid. 80000000 00000000 272e194a d2411890\nWSQCQDT@:80000000 00000000 272e194a d2411890\nWSQPAS@: 80000000 00000000 272e194a d2000a00\nCURSOR NAME IS FILE \nSTMT NAME IS FIFAATTALL0004 \nPACKAGE NAME IS in
library \nPROBLEM WITH QDT FOR STMT# 18, QDT# 1, OCLE 1\nQDT@:80000000 00000000 272e194a d2411890\nWSQCQDT@:80000000 00000000 272e194a d2411890\nWSQPAS@: 80000000 00000000 272e194a d2000a00\nCURSOR NAME IS FILE \nSTMT NAME IS FIFAATTALL0004 \nPACKAGE NAME IS in
library \nPROBLE Dump output directed to spooled file 156, job 030309/QUSER/QZDASOINIT

Some of these dumps are thousands of pages long. All in (to me) unreadable Hex. Not much use.

The System is V5R4M0. They are on DB Group 13 (!)

I know *something* is amiss here but I can't see the SQL statements that are causing the dumps. More interesting is the fact the application does work (albeit slowly). The tables are properly created/read/updated/deleted. But something is definitely amiss. Where should I start?

Pete