Paul Russell , Aug 13, 2010; 05:13 a.m.
Bad news mate. 30s is the maximum timed exposure on the 50D and most other DSLRs.
A few options present themselves:
Use EOS utility via tethered capture for longer exposures.
Use the expensive Canon timer remote.
Use a cheapo chinese made copy (works well on my 7D)
Use a regular remote with the shutter lock and the LCD topscreen counter.