Since there is no amount limit for number of characters in Squad URL you can put large enough text into Squad URL when editing/creating profile and it can freeze your computer. Different PC hardware will probably handle different amounts of text.
Spec of my PC:
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
6.00 GB RAM
ATI Radeon HD 3870 X2
279 GB HDD