# Issue with PathGraph

I am having a strange issue with PathGraph. Executing

PathGraph[{a, b, c}]


or PathGraph[{1,2,3}], etc., returns a path-graph with three vertices as expected. However, executing:

In[10]:= PathGraph[{v1, v2, v3}]
Out[10]= PathGraph[{v1, v2, v3}]


That is, it stays unevaluated instead of returning the Graph object. I tried several variations and apparently the issue occurs whenever v2 is among the vertices. That is all of PathGraph[{a1, v2, a3}], PathGraph[{v2, x}], PathGraph[{1, 2, v2, x}], etc. remain unevaluated after execution.

I tried this on two computers, both with clean Kernels (with no definitions made or packages loaded, etc.).

Mathematica version: 8.0.0.0

Can anyone reproduce this? Is this a bug?

Update: This is working correctly in version 9.

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I can repro this one. Awful. –  belisarius Jun 3 '12 at 4:59
Me too. Also, neither of these work either: PathGraph[{j, k, l}]; PathGraph[{v, w, x}] –  Jagra Jun 3 '12 at 5:07
Daniel Lichtblau has, on several occasions, commented/answered saying that such bugs are often caused by some internal variable sorting or issues with hashing. There is no way to predict which ones will fail, but they fix them as they find them. Here's a rather nasty bug on versions 7 and below (fixed in 8 onwards) that's somewhat related. I'd suggest emailing to support@wolfram.com –  rm -rf Jun 3 '12 at 5:21
I emailed them. Waiting for reply. –  becko Jun 3 '12 at 16:10
@becko Please share the reply when you get one. –  Szabolcs Jun 4 '12 at 7:19

This is definitely a bug. I emailed Wolfram support and got the following reply:

Hello,