Ah... makes sense. What are you using?
I'm using the solo mining software my FPGA cluster came with, and I'm pointing it to Stratum Proxy.
Here's what happens when I try to connect to EMC compared to Slush's pool:
EMC:root@5-1:~/stratum-mining-proxy# ./mining_proxy.py -o 208.110.68.114 -p 3333 -v
2012-11-13 19:18:58,067 INFO proxy jobs.<module> # C extension for midstate not available. Using default implementation instead.
2012-11-13 19:18:58,069 INFO proxy mining_proxy.main # Stratum proxy version: 1.1.1
2012-11-13 19:18:58,070 INFO proxy mining_proxy.main # Trying to connect to Stratum pool at 208.110.68.114:3333
2012-11-13 19:18:58,278 INFO stats stats.print_stats # 1 peers connected, state changed 1 times
2012-11-13 19:18:58,278 INFO proxy mining_proxy.on_connect # Connected to Stratum pool at 208.110.68.114:3333
2012-11-13 19:18:58,279 INFO proxy mining_proxy.on_connect # Subscribing for mining jobs
2012-11-13 19:18:58,502 INFO proxy mining_proxy.on_disconnect # Disconnected from Stratum pool at 208.110.68.114:3333
2012-11-13 19:18:58,502 INFO stats stats.print_stats # 0 peers connected, state changed 1 times
^C2012-11-13 19:19:00,793 INFO proxy mining_proxy.on_shutdown # Shutting down proxy...
Slush:root@5-1:~/stratum-mining-proxy# ./mining_proxy.py -v
2012-11-13 19:19:07,355 INFO proxy jobs.<module> # C extension for midstate not available. Using default implementation instead.
2012-11-13 19:19:07,357 INFO proxy mining_proxy.main # Stratum proxy version: 1.1.1
2012-11-13 19:19:07,357 INFO proxy mining_proxy.main # Trying to connect to Stratum pool at api-stratum.bitcoin.cz:3333
2012-11-13 19:19:07,487 INFO stats stats.print_stats # 1 peers connected, state changed 1 times
2012-11-13 19:19:07,487 INFO proxy mining_proxy.on_connect # Connected to Stratum pool at api-stratum.bitcoin.cz:3333
2012-11-13 19:19:07,488 INFO proxy mining_proxy.on_connect # Subscribing for mining jobs
2012-11-13 19:19:07,594 INFO proxy mining_proxy.main # -----------------------------------------------------------------------
2012-11-13 19:19:07,594 INFO proxy mining_proxy.main # PROXY IS LISTENING ON ALL IPs ON PORT 3333 (stratum) AND 8332 (getwork)
2012-11-13 19:19:07,595 INFO proxy mining_proxy.main # -----------------------------------------------------------------------
2012-11-13 19:19:07,598 INFO proxy client_service.handle_event # New job 1117e for prevhash dcf34271, clean_jobs=True