I was connected to a cat 3750 via telnet. The only connection/port live to that switch is to a 3550 (doing L2).
Then when I did 'ip routing', I lost connection via telnet to the 3750 and now I can't get connected to that switch anymore.
My question is, is there any chance that the 'ip routing' config will cause a loop in the remote network? Again, that switch was configured with a default configuration (other than the vlan1 configured there).
It is almost certainly not an issue about a loop (without more detailed information about the topology and the operating environment I would not be able to say for sure that there is no loop). Sundar is almost certainly right that the issue is that before you enabled ip routing the switch had an ip default-gateway which allowed it to access remote subnets. When you enable ip routing it effectively disables the ip default-gateway and without a default route you lost connectivity. Have someone configure an appropriate default route and your connectivity will be restored.